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Timestamp:
01/21/25 03:08:24 (3 days ago)
Author:
stefan toskovski <stefantoska84@…>
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main
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Message:

F4 Finalna Verzija

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  • imaps-frontend/node_modules/ajv/README.md

    r0c6b92a r79a0317  
    1 <img align="right" alt="Ajv logo" width="160" src="https://ajv.js.org/images/ajv_logo.png">
    2 
    3 # Ajv: Another JSON Schema Validator
    4 
    5 The fastest JSON Schema validator for Node.js and browser. Supports draft-04/06/07.
    6 
    7 [![Build Status](https://travis-ci.org/ajv-validator/ajv.svg?branch=master)](https://travis-ci.org/ajv-validator/ajv)
     1<img align="right" alt="Ajv logo" width="160" src="https://ajv.js.org/img/ajv.svg">
     2
     3&nbsp;
     4
     5# Ajv JSON schema validator
     6
     7The fastest JSON validator for Node.js and browser.
     8
     9Supports JSON Schema draft-04/06/07/2019-09/2020-12 ([draft-04 support](https://ajv.js.org/json-schema.html#draft-04) requires ajv-draft-04 package) and JSON Type Definition [RFC8927](https://datatracker.ietf.org/doc/rfc8927/).
     10
     11[![build](https://github.com/ajv-validator/ajv/actions/workflows/build.yml/badge.svg)](https://github.com/ajv-validator/ajv/actions?query=workflow%3Abuild)
    812[![npm](https://img.shields.io/npm/v/ajv.svg)](https://www.npmjs.com/package/ajv)
    9 [![npm (beta)](https://img.shields.io/npm/v/ajv/beta)](https://www.npmjs.com/package/ajv/v/7.0.0-beta.0)
    1013[![npm downloads](https://img.shields.io/npm/dm/ajv.svg)](https://www.npmjs.com/package/ajv)
    1114[![Coverage Status](https://coveralls.io/repos/github/ajv-validator/ajv/badge.svg?branch=master)](https://coveralls.io/github/ajv-validator/ajv?branch=master)
     15[![SimpleX](https://img.shields.io/badge/chat-on%20SimpleX-70F0F9)](https://simplex.chat/contact#/?v=1-2&smp=smp%3A%2F%2Fu2dS9sG8nMNURyZwqASV4yROM28Er0luVTx5X1CsMrU%3D%40smp4.simplex.im%2F8KvvURM6J38Gdq9dCuPswMOkMny0xCOJ%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAr8rPVRuMOXv6kwF2yUAap-eoVg-9ssOFCi1fIrxTUw0%253D%26srv%3Do5vmywmrnaxalvz6wi3zicyftgio6psuvyniis6gco6bp6ekl4cqj4id.onion&data=%7B%22type%22%3A%22group%22%2C%22groupLinkId%22%3A%224pwLRgWHU9tlroMWHz0uOg%3D%3D%22%7D)
    1216[![Gitter](https://img.shields.io/gitter/room/ajv-validator/ajv.svg)](https://gitter.im/ajv-validator/ajv)
    1317[![GitHub Sponsors](https://img.shields.io/badge/$-sponsors-brightgreen)](https://github.com/sponsors/epoberezkin)
    1418
    15 
    16 ## Ajv v7 beta is released
    17 
    18 [Ajv version 7.0.0-beta.0](https://github.com/ajv-validator/ajv/tree/v7-beta) is released with these changes:
    19 
    20 - to reduce the mistakes in JSON schemas and unexpected validation results, [strict mode](./docs/strict-mode.md) is added - it prohibits ignored or ambiguous JSON Schema elements.
    21 - to make code injection from untrusted schemas impossible, [code generation](./docs/codegen.md) is fully re-written to be safe.
    22 - to simplify Ajv extensions, the new keyword API that is used by pre-defined keywords is available to user-defined keywords - it is much easier to define any keywords now, especially with subschemas.
    23 - schemas are compiled to ES6 code (ES5 code generation is supported with an option).
    24 - to improve reliability and maintainability the code is migrated to TypeScript.
    25 
    26 **Please note**:
    27 
    28 - the support for JSON-Schema draft-04 is removed - if you have schemas using "id" attributes you have to replace them with "\$id" (or continue using version 6 that will be supported until 02/28/2021).
    29 - all formats are separated to ajv-formats package - they have to be explicitely added if you use them.
    30 
    31 See [release notes](https://github.com/ajv-validator/ajv/releases/tag/v7.0.0-beta.0) for the details.
    32 
    33 To install the new version:
    34 
    35 ```bash
    36 npm install ajv@beta
    37 ```
    38 
    39 See [Getting started with v7](https://github.com/ajv-validator/ajv/tree/v7-beta#usage) for code example.
    40 
    41 
    42 ## Mozilla MOSS grant and OpenJS Foundation
    43 
    44 [<img src="https://www.poberezkin.com/images/mozilla.png" width="240" height="68">](https://www.mozilla.org/en-US/moss/) &nbsp;&nbsp;&nbsp; [<img src="https://www.poberezkin.com/images/openjs.png" width="220" height="68">](https://openjsf.org/blog/2020/08/14/ajv-joins-openjs-foundation-as-an-incubation-project/)
    45 
    46 Ajv has been awarded a grant from Mozilla’s [Open Source Support (MOSS) program](https://www.mozilla.org/en-US/moss/) in the “Foundational Technology” track! It will sponsor the development of Ajv support of [JSON Schema version 2019-09](https://tools.ietf.org/html/draft-handrews-json-schema-02) and of [JSON Type Definition](https://tools.ietf.org/html/draft-ucarion-json-type-definition-04).
    47 
    48 Ajv also joined [OpenJS Foundation](https://openjsf.org/) – having this support will help ensure the longevity and stability of Ajv for all its users.
    49 
    50 This [blog post](https://www.poberezkin.com/posts/2020-08-14-ajv-json-validator-mozilla-open-source-grant-openjs-foundation.html) has more details.
    51 
    52 I am looking for the long term maintainers of Ajv – working with [ReadySet](https://www.thereadyset.co/), also sponsored by Mozilla, to establish clear guidelines for the role of a "maintainer" and the contribution standards, and to encourage a wider, more inclusive, contribution from the community.
    53 
    54 
    55 ## Please [sponsor Ajv development](https://github.com/sponsors/epoberezkin)
     19## Ajv sponsors
     20
     21[<img src="https://ajv.js.org/img/mozilla.svg" width="45%" alt="Mozilla">](https://www.mozilla.org)<img src="https://ajv.js.org/img/gap.svg" width="9%">[<img src="https://ajv.js.org/img/reserved.svg" width="45%">](https://opencollective.com/ajv)
     22
     23[<img src="https://ajv.js.org/img/microsoft.png" width="31%" alt="Microsoft">](https://opensource.microsoft.com)<img src="https://ajv.js.org/img/gap.svg" width="3%">[<img src="https://ajv.js.org/img/reserved.svg" width="31%">](https://opencollective.com/ajv)<img src="https://ajv.js.org/img/gap.svg" width="3%">[<img src="https://ajv.js.org/img/reserved.svg" width="31%">](https://opencollective.com/ajv)
     24
     25[<img src="https://ajv.js.org/img/retool.svg" width="22.5%" alt="Retool">](https://retool.com/?utm_source=sponsor&utm_campaign=ajv)<img src="https://ajv.js.org/img/gap.svg" width="3%">[<img src="https://ajv.js.org/img/tidelift.svg" width="22.5%" alt="Tidelift">](https://tidelift.com/subscription/pkg/npm-ajv?utm_source=npm-ajv&utm_medium=referral&utm_campaign=enterprise)<img src="https://ajv.js.org/img/gap.svg" width="3%">[<img src="https://ajv.js.org/img/simplex.svg" width="22.5%" alt="SimpleX">](https://github.com/simplex-chat/simplex-chat)<img src="https://ajv.js.org/img/gap.svg" width="3%">[<img src="https://ajv.js.org/img/reserved.svg" width="22.5%">](https://opencollective.com/ajv)
     26
     27## Contributing
     28
     29More than 100 people contributed to Ajv, and we would love to have you join the development. We welcome implementing new features that will benefit many users and ideas to improve our documentation.
     30
     31Please review [Contributing guidelines](./CONTRIBUTING.md) and [Code components](https://ajv.js.org/components.html).
     32
     33## Documentation
     34
     35All documentation is available on the [Ajv website](https://ajv.js.org).
     36
     37Some useful site links:
     38
     39- [Getting started](https://ajv.js.org/guide/getting-started.html)
     40- [JSON Schema vs JSON Type Definition](https://ajv.js.org/guide/schema-language.html)
     41- [API reference](https://ajv.js.org/api.html)
     42- [Strict mode](https://ajv.js.org/strict-mode.html)
     43- [Standalone validation code](https://ajv.js.org/standalone.html)
     44- [Security considerations](https://ajv.js.org/security.html)
     45- [Command line interface](https://ajv.js.org/packages/ajv-cli.html)
     46- [Frequently Asked Questions](https://ajv.js.org/faq.html)
     47
     48## <a name="sponsors"></a>Please [sponsor Ajv development](https://github.com/sponsors/epoberezkin)
    5649
    5750Since I asked to support Ajv development 40 people and 6 organizations contributed via GitHub and OpenCollective - this support helped receiving the MOSS grant!
    … …  
    6053
    6154Please sponsor Ajv via:
     55
    6256- [GitHub sponsors page](https://github.com/sponsors/epoberezkin) (GitHub will match it)
    63 - [Ajv Open Collective️](https://opencollective.com/ajv)
     57- [Ajv Open Collective](https://opencollective.com/ajv)
    6458
    6559Thank you.
    66 
    6760
    6861#### Open Collective sponsors
    … …  
    8073<a href="https://opencollective.com/ajv/organization/8/website"><img src="https://opencollective.com/ajv/organization/8/avatar.svg"></a>
    8174<a href="https://opencollective.com/ajv/organization/9/website"><img src="https://opencollective.com/ajv/organization/9/avatar.svg"></a>
    82 
    83 
    84 ## Using version 6
    85 
    86 [JSON Schema draft-07](http://json-schema.org/latest/json-schema-validation.html) is published.
    87 
    88 [Ajv version 6.0.0](https://github.com/ajv-validator/ajv/releases/tag/v6.0.0) that supports draft-07 is released. It may require either migrating your schemas or updating your code (to continue using draft-04 and v5 schemas, draft-06 schemas will be supported without changes).
    89 
    90 __Please note__: To use Ajv with draft-06 schemas you need to explicitly add the meta-schema to the validator instance:
    91 
    92 ```javascript
    93 ajv.addMetaSchema(require('ajv/lib/refs/json-schema-draft-06.json'));
    94 ```
    95 
    96 To use Ajv with draft-04 schemas in addition to explicitly adding meta-schema you also need to use option schemaId:
    97 
    98 ```javascript
    99 var ajv = new Ajv({schemaId: 'id'});
    100 // If you want to use both draft-04 and draft-06/07 schemas:
    101 // var ajv = new Ajv({schemaId: 'auto'});
    102 ajv.addMetaSchema(require('ajv/lib/refs/json-schema-draft-04.json'));
    103 ```
    104 
    105 
    106 ## Contents
    107 
    108 - [Performance](#performance)
    109 - [Features](#features)
    110 - [Getting started](#getting-started)
    111 - [Frequently Asked Questions](https://github.com/ajv-validator/ajv/blob/master/FAQ.md)
    112 - [Using in browser](#using-in-browser)
    113   - [Ajv and Content Security Policies (CSP)](#ajv-and-content-security-policies-csp)
    114 - [Command line interface](#command-line-interface)
    115 - Validation
    116   - [Keywords](#validation-keywords)
    117   - [Annotation keywords](#annotation-keywords)
    118   - [Formats](#formats)
    119   - [Combining schemas with $ref](#ref)
    120   - [$data reference](#data-reference)
    121   - NEW: [$merge and $patch keywords](#merge-and-patch-keywords)
    122   - [Defining custom keywords](#defining-custom-keywords)
    123   - [Asynchronous schema compilation](#asynchronous-schema-compilation)
    124   - [Asynchronous validation](#asynchronous-validation)
    125 - [Security considerations](#security-considerations)
    126   - [Security contact](#security-contact)
    127   - [Untrusted schemas](#untrusted-schemas)
    128   - [Circular references in objects](#circular-references-in-javascript-objects)
    129   - [Trusted schemas](#security-risks-of-trusted-schemas)
    130   - [ReDoS attack](#redos-attack)
    131 - Modifying data during validation
    132   - [Filtering data](#filtering-data)
    133   - [Assigning defaults](#assigning-defaults)
    134   - [Coercing data types](#coercing-data-types)
    135 - API
    136   - [Methods](#api)
    137   - [Options](#options)
    138   - [Validation errors](#validation-errors)
    139 - [Plugins](#plugins)
    140 - [Related packages](#related-packages)
    141 - [Some packages using Ajv](#some-packages-using-ajv)
    142 - [Tests, Contributing, Changes history](#tests)
    143 - [Support, Code of conduct, License](#open-source-software-support)
    144 
     75<a href="https://opencollective.com/ajv/organization/10/website"><img src="https://opencollective.com/ajv/organization/10/avatar.svg"></a>
     76<a href="https://opencollective.com/ajv/organization/11/website"><img src="https://opencollective.com/ajv/organization/11/avatar.svg"></a>
     77<a href="https://opencollective.com/ajv/organization/12/website"><img src="https://opencollective.com/ajv/organization/12/avatar.svg"></a>
     78<a href="https://opencollective.com/ajv/organization/13/website"><img src="https://opencollective.com/ajv/organization/13/avatar.svg"></a>
     79<a href="https://opencollective.com/ajv/organization/14/website"><img src="https://opencollective.com/ajv/organization/14/avatar.svg"></a>
     80<a href="https://opencollective.com/ajv/organization/15/website"><img src="https://opencollective.com/ajv/organization/15/avatar.svg"></a>
     81<a href="https://opencollective.com/ajv/organization/16/website"><img src="https://opencollective.com/ajv/organization/16/avatar.svg"></a>
     82<a href="https://opencollective.com/ajv/organization/17/website"><img src="https://opencollective.com/ajv/organization/17/avatar.svg"></a>
     83<a href="https://opencollective.com/ajv/organization/18/website"><img src="https://opencollective.com/ajv/organization/18/avatar.svg"></a>
     84<a href="https://opencollective.com/ajv/organization/19/website"><img src="https://opencollective.com/ajv/organization/19/avatar.svg"></a>
     85<a href="https://opencollective.com/ajv/organization/20/website"><img src="https://opencollective.com/ajv/organization/20/avatar.svg"></a>
     86<a href="https://opencollective.com/ajv/organization/21/website"><img src="https://opencollective.com/ajv/organization/21/avatar.svg"></a>
     87<a href="https://opencollective.com/ajv/organization/22/website"><img src="https://opencollective.com/ajv/organization/22/avatar.svg"></a>
     88<a href="https://opencollective.com/ajv/organization/23/website"><img src="https://opencollective.com/ajv/organization/23/avatar.svg"></a>
     89<a href="https://opencollective.com/ajv/organization/24/website"><img src="https://opencollective.com/ajv/organization/24/avatar.svg"></a>
    14590
    14691## Performance
    14792
    148 Ajv generates code using [doT templates](https://github.com/olado/doT) to turn JSON Schemas into super-fast validation functions that are efficient for v8 optimization.
     93Ajv generates code to turn JSON Schemas into super-fast validation functions that are efficient for v8 optimization.
    14994
    15095Currently Ajv is the fastest and the most standard compliant validator according to these benchmarks:
    … …  
    155100- [themis benchmark](https://cdn.rawgit.com/playlyfe/themis/master/benchmark/results.html)
    156101
    157 
    158102Performance of different validators by [json-schema-benchmark](https://github.com/ebdrup/json-schema-benchmark):
    159103
    160 [![performance](https://chart.googleapis.com/chart?chxt=x,y&cht=bhs&chco=76A4FB&chls=2.0&chbh=32,4,1&chs=600x416&chxl=-1:|djv|ajv|json-schema-validator-generator|jsen|is-my-json-valid|themis|z-schema|jsck|skeemas|json-schema-library|tv4&chd=t:100,98,72.1,66.8,50.1,15.1,6.1,3.8,1.2,0.7,0.2)](https://github.com/ebdrup/json-schema-benchmark/blob/master/README.md#performance)
    161 
     104[![performance](https://chart.googleapis.com/chart?chxt=x,y&cht=bhs&chco=76A4FB&chls=2.0&chbh=62,4,1&chs=600x416&chxl=-1:|ajv|@exodus/schemasafe|is-my-json-valid|djv|@cfworker/json-schema|jsonschema/=t:100,69.2,51.5,13.1,5.1,1.2)](https://github.com/ebdrup/json-schema-benchmark/blob/master/README.md#performance)
    162105
    163106## Features
    164107
    165 - Ajv implements full JSON Schema [draft-06/07](http://json-schema.org/) and draft-04 standards:
    166   - all validation keywords (see [JSON Schema validation keywords](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md))
    167   - full support of remote refs (remote schemas have to be added with `addSchema` or compiled to be available)
    168   - support of circular references between schemas
    169   - correct string lengths for strings with unicode pairs (can be turned off)
    170   - [formats](#formats) defined by JSON Schema draft-07 standard and custom formats (can be turned off)
    171   - [validates schemas against meta-schema](#api-validateschema)
    172 - supports [browsers](#using-in-browser) and Node.js 0.10-14.x
    173 - [asynchronous loading](#asynchronous-schema-compilation) of referenced schemas during compilation
    174 - "All errors" validation mode with [option allErrors](#options)
    175 - [error messages with parameters](#validation-errors) describing error reasons to allow creating custom error messages
     108- Ajv implements JSON Schema [draft-06/07/2019-09/2020-12](http://json-schema.org/) standards (draft-04 is supported in v6):
     109  - all validation keywords (see [JSON Schema validation keywords](https://ajv.js.org/json-schema.html))
     110  - [OpenAPI](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md) extensions:
     111    - NEW: keyword [discriminator](https://ajv.js.org/json-schema.html#discriminator).
     112    - keyword [nullable](https://ajv.js.org/json-schema.html#nullable).
     113  - full support of remote references (remote schemas have to be added with `addSchema` or compiled to be available)
     114  - support of recursive references between schemas
     115  - correct string lengths for strings with unicode pairs
     116  - JSON Schema [formats](https://ajv.js.org/guide/formats.html) (with [ajv-formats](https://github.com/ajv-validator/ajv-formats) plugin).
     117  - [validates schemas against meta-schema](https://ajv.js.org/api.html#api-validateschema)
     118- NEW: supports [JSON Type Definition](https://datatracker.ietf.org/doc/rfc8927/):
     119  - all keywords (see [JSON Type Definition schema forms](https://ajv.js.org/json-type-definition.html))
     120  - meta-schema for JTD schemas
     121  - "union" keyword and user-defined keywords (can be used inside "metadata" member of the schema)
     122- supports [browsers](https://ajv.js.org/guide/environments.html#browsers) and Node.js 10.x - current
     123- [asynchronous loading](https://ajv.js.org/guide/managing-schemas.html#asynchronous-schema-loading) of referenced schemas during compilation
     124- "All errors" validation mode with [option allErrors](https://ajv.js.org/options.html#allerrors)
     125- [error messages with parameters](https://ajv.js.org/api.html#validation-errors) describing error reasons to allow error message generation
    176126- i18n error messages support with [ajv-i18n](https://github.com/ajv-validator/ajv-i18n) package
    177 - [filtering data](#filtering-data) from additional properties
    178 - [assigning defaults](#assigning-defaults) to missing properties and items
    179 - [coercing data](#coercing-data-types) to the types specified in `type` keywords
    180 - [custom keywords](#defining-custom-keywords)
    181 - draft-06/07 keywords `const`, `contains`, `propertyNames` and `if/then/else`
    182 - draft-06 boolean schemas (`true`/`false` as a schema to always pass/fail).
    183 - keywords `switch`, `patternRequired`, `formatMaximum` / `formatMinimum` and `formatExclusiveMaximum` / `formatExclusiveMinimum` from [JSON Schema extension proposals](https://github.com/json-schema/json-schema/wiki/v5-Proposals) with [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package
    184 - [$data reference](#data-reference) to use values from the validated data as values for the schema keywords
    185 - [asynchronous validation](#asynchronous-validation) of custom formats and keywords
    186 
     127- [removing-additional-properties](https://ajv.js.org/guide/modifying-data.html#removing-additional-properties)
     128- [assigning defaults](https://ajv.js.org/guide/modifying-data.html#assigning-defaults) to missing properties and items
     129- [coercing data](https://ajv.js.org/guide/modifying-data.html#coercing-data-types) to the types specified in `type` keywords
     130- [user-defined keywords](https://ajv.js.org/guide/user-keywords.html)
     131- additional extension keywords with [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package
     132- [\$data reference](https://ajv.js.org/guide/combining-schemas.html#data-reference) to use values from the validated data as values for the schema keywords
     133- [asynchronous validation](https://ajv.js.org/guide/async-validation.html) of user-defined formats and keywords
    187134
    188135## Install
     136
     137To install version 8:
    189138
    190139```
    … …  
    192141```
    193142
    194 
    195143## <a name="usage"></a>Getting started
    196144
    197 Try it in the Node.js REPL: https://tonicdev.com/npm/ajv
    198 
    199 
    200 The fastest validation call:
     145Try it in the Node.js REPL: https://runkit.com/npm/ajv
     146
     147In JavaScript:
    201148
    202149```javascript
     150// or ESM/TypeScript import
     151import Ajv from "ajv"
    203152// Node.js require:
    204 var Ajv = require('ajv');
    205 // or ESM/TypeScript import
    206 import Ajv from 'ajv';
    207 
    208 var ajv = new Ajv(); // options can be passed, e.g. {allErrors: true}
    209 var validate = ajv.compile(schema);
    210 var valid = validate(data);
    211 if (!valid) console.log(validate.errors);
     153const Ajv = require("ajv")
     154
     155const ajv = new Ajv() // options can be passed, e.g. {allErrors: true}
     156
     157const schema = {
     158  type: "object",
     159  properties: {
     160    foo: {type: "integer"},
     161    bar: {type: "string"},
     162  },
     163  required: ["foo"],
     164  additionalProperties: false,
     165}
     166
     167const data = {
     168  foo: 1,
     169  bar: "abc",
     170}
     171
     172const validate = ajv.compile(schema)
     173const valid = validate(data)
     174if (!valid) console.log(validate.errors)
    212175```
    213176
    214 or with less code
    215 
    216 ```javascript
    217 // ...
    218 var valid = ajv.validate(schema, data);
    219 if (!valid) console.log(ajv.errors);
    220 // ...
    221 ```
    222 
    223 or
    224 
    225 ```javascript
    226 // ...
    227 var valid = ajv.addSchema(schema, 'mySchema')
    228                .validate('mySchema', data);
    229 if (!valid) console.log(ajv.errorsText());
    230 // ...
    231 ```
    232 
    233 See [API](#api) and [Options](#options) for more details.
    234 
    235 Ajv compiles schemas to functions and caches them in all cases (using schema serialized with [fast-json-stable-stringify](https://github.com/epoberezkin/fast-json-stable-stringify) or a custom function as a key), so that the next time the same schema is used (not necessarily the same object instance) it won't be compiled again.
    236 
    237 The best performance is achieved when using compiled functions returned by `compile` or `getSchema` methods (there is no additional function call).
    238 
    239 __Please note__: every time a validation function or `ajv.validate` are called `errors` property is overwritten. You need to copy `errors` array reference to another variable if you want to use it later (e.g., in the callback). See [Validation errors](#validation-errors)
    240 
    241 __Note for TypeScript users__: `ajv` provides its own TypeScript declarations
    242 out of the box, so you don't need to install the deprecated `@types/ajv`
    243 module.
    244 
    245 
    246 ## Using in browser
    247 
    248 You can require Ajv directly from the code you browserify - in this case Ajv will be a part of your bundle.
    249 
    250 If you need to use Ajv in several bundles you can create a separate UMD bundle using `npm run bundle` script (thanks to [siddo420](https://github.com/siddo420)).
    251 
    252 Then you need to load Ajv in the browser:
    253 ```html
    254 <script src="ajv.min.js"></script>
    255 ```
    256 
    257 This bundle can be used with different module systems; it creates global `Ajv` if no module system is found.
    258 
    259 The browser bundle is available on [cdnjs](https://cdnjs.com/libraries/ajv).
    260 
    261 Ajv is tested with these browsers:
    262 
    263 [![Sauce Test Status](https://saucelabs.com/browser-matrix/epoberezkin.svg)](https://saucelabs.com/u/epoberezkin)
    264 
    265 __Please note__: some frameworks, e.g. Dojo, may redefine global require in such way that is not compatible with CommonJS module format. In such case Ajv bundle has to be loaded before the framework and then you can use global Ajv (see issue [#234](https://github.com/ajv-validator/ajv/issues/234)).
    266 
    267 
    268 ### Ajv and Content Security Policies (CSP)
    269 
    270 If you're using Ajv to compile a schema (the typical use) in a browser document that is loaded with a Content Security Policy (CSP), that policy will require a `script-src` directive that includes the value `'unsafe-eval'`.
    271 :warning: NOTE, however, that `unsafe-eval` is NOT recommended in a secure CSP[[1]](https://developer.chrome.com/extensions/contentSecurityPolicy#relaxing-eval), as it has the potential to open the document to cross-site scripting (XSS) attacks.
    272 
    273 In order to make use of Ajv without easing your CSP, you can [pre-compile a schema using the CLI](https://github.com/ajv-validator/ajv-cli#compile-schemas). This will transpile the schema JSON into a JavaScript file that exports a `validate` function that works simlarly to a schema compiled at runtime.
    274 
    275 Note that pre-compilation of schemas is performed using [ajv-pack](https://github.com/ajv-validator/ajv-pack) and there are [some limitations to the schema features it can compile](https://github.com/ajv-validator/ajv-pack#limitations). A successfully pre-compiled schema is equivalent to the same schema compiled at runtime.
    276 
    277 
    278 ## Command line interface
    279 
    280 CLI is available as a separate npm package [ajv-cli](https://github.com/ajv-validator/ajv-cli). It supports:
    281 
    282 - compiling JSON Schemas to test their validity
    283 - BETA: generating standalone module exporting a validation function to be used without Ajv (using [ajv-pack](https://github.com/ajv-validator/ajv-pack))
    284 - migrate schemas to draft-07 (using [json-schema-migrate](https://github.com/epoberezkin/json-schema-migrate))
    285 - validating data file(s) against JSON Schema
    286 - testing expected validity of data against JSON Schema
    287 - referenced schemas
    288 - custom meta-schemas
    289 - files in JSON, JSON5, YAML, and JavaScript format
    290 - all Ajv options
    291 - reporting changes in data after validation in [JSON-patch](https://tools.ietf.org/html/rfc6902) format
    292 
    293 
    294 ## Validation keywords
    295 
    296 Ajv supports all validation keywords from draft-07 of JSON Schema standard:
    297 
    298 - [type](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#type)
    299 - [for numbers](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#keywords-for-numbers) - maximum, minimum, exclusiveMaximum, exclusiveMinimum, multipleOf
    300 - [for strings](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#keywords-for-strings) - maxLength, minLength, pattern, format
    301 - [for arrays](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#keywords-for-arrays) - maxItems, minItems, uniqueItems, items, additionalItems, [contains](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#contains)
    302 - [for objects](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#keywords-for-objects) - maxProperties, minProperties, required, properties, patternProperties, additionalProperties, dependencies, [propertyNames](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#propertynames)
    303 - [for all types](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#keywords-for-all-types) - enum, [const](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#const)
    304 - [compound keywords](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#compound-keywords) - not, oneOf, anyOf, allOf, [if/then/else](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#ifthenelse)
    305 
    306 With [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package Ajv also supports validation keywords from [JSON Schema extension proposals](https://github.com/json-schema/json-schema/wiki/v5-Proposals) for JSON Schema standard:
    307 
    308 - [patternRequired](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#patternrequired-proposed) - like `required` but with patterns that some property should match.
    309 - [formatMaximum, formatMinimum, formatExclusiveMaximum, formatExclusiveMinimum](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md#formatmaximum--formatminimum-and-exclusiveformatmaximum--exclusiveformatminimum-proposed) - setting limits for date, time, etc.
    310 
    311 See [JSON Schema validation keywords](https://github.com/ajv-validator/ajv/blob/master/KEYWORDS.md) for more details.
    312 
    313 
    314 ## Annotation keywords
    315 
    316 JSON Schema specification defines several annotation keywords that describe schema itself but do not perform any validation.
    317 
    318 - `title` and `description`: information about the data represented by that schema
    319 - `$comment` (NEW in draft-07): information for developers. With option `$comment` Ajv logs or passes the comment string to the user-supplied function. See [Options](#options).
    320 - `default`: a default value of the data instance, see [Assigning defaults](#assigning-defaults).
    321 - `examples` (NEW in draft-06): an array of data instances. Ajv does not check the validity of these instances against the schema.
    322 - `readOnly` and `writeOnly` (NEW in draft-07): marks data-instance as read-only or write-only in relation to the source of the data (database, api, etc.).
    323 - `contentEncoding`: [RFC 2045](https://tools.ietf.org/html/rfc2045#section-6.1 ), e.g., "base64".
    324 - `contentMediaType`: [RFC 2046](https://tools.ietf.org/html/rfc2046), e.g., "image/png".
    325 
    326 __Please note__:  Ajv does not implement validation of the keywords `examples`, `contentEncoding` and `contentMediaType` but it reserves them. If you want to create a plugin that implements some of them, it should remove these keywords from the instance.
    327 
    328 
    329 ## Formats
    330 
    331 Ajv implements formats defined by JSON Schema specification and several other formats. It is recommended NOT to use "format" keyword implementations with untrusted data, as they use potentially unsafe regular expressions - see [ReDoS attack](#redos-attack).
    332 
    333 __Please note__: if you need to use "format" keyword to validate untrusted data, you MUST assess their suitability and safety for your validation scenarios.
    334 
    335 The following formats are implemented for string validation with "format" keyword:
    336 
    337 - _date_: full-date according to [RFC3339](http://tools.ietf.org/html/rfc3339#section-5.6).
    338 - _time_: time with optional time-zone.
    339 - _date-time_: date-time from the same source (time-zone is mandatory). `date`, `time` and `date-time` validate ranges in `full` mode and only regexp in `fast` mode (see [options](#options)).
    340 - _uri_: full URI.
    341 - _uri-reference_: URI reference, including full and relative URIs.
    342 - _uri-template_: URI template according to [RFC6570](https://tools.ietf.org/html/rfc6570)
    343 - _url_ (deprecated): [URL record](https://url.spec.whatwg.org/#concept-url).
    344 - _email_: email address.
    345 - _hostname_: host name according to [RFC1034](http://tools.ietf.org/html/rfc1034#section-3.5).
    346 - _ipv4_: IP address v4.
    347 - _ipv6_: IP address v6.
    348 - _regex_: tests whether a string is a valid regular expression by passing it to RegExp constructor.
    349 - _uuid_: Universally Unique IDentifier according to [RFC4122](http://tools.ietf.org/html/rfc4122).
    350 - _json-pointer_: JSON-pointer according to [RFC6901](https://tools.ietf.org/html/rfc6901).
    351 - _relative-json-pointer_: relative JSON-pointer according to [this draft](http://tools.ietf.org/html/draft-luff-relative-json-pointer-00).
    352 
    353 __Please note__: JSON Schema draft-07 also defines formats `iri`, `iri-reference`, `idn-hostname` and `idn-email` for URLs, hostnames and emails with international characters. Ajv does not implement these formats. If you create Ajv plugin that implements them please make a PR to mention this plugin here.
    354 
    355 There are two modes of format validation: `fast` and `full`. This mode affects formats `date`, `time`, `date-time`, `uri`, `uri-reference`, and `email`. See [Options](#options) for details.
    356 
    357 You can add additional formats and replace any of the formats above using [addFormat](#api-addformat) method.
    358 
    359 The option `unknownFormats` allows changing the default behaviour when an unknown format is encountered. In this case Ajv can either fail schema compilation (default) or ignore it (default in versions before 5.0.0). You also can allow specific format(s) that will be ignored. See [Options](#options) for details.
    360 
    361 You can find regular expressions used for format validation and the sources that were used in [formats.js](https://github.com/ajv-validator/ajv/blob/master/lib/compile/formats.js).
    362 
    363 
    364 ## <a name="ref"></a>Combining schemas with $ref
    365 
    366 You can structure your validation logic across multiple schema files and have schemas reference each other using `$ref` keyword.
    367 
    368 Example:
    369 
    370 ```javascript
    371 var schema = {
    372   "$id": "http://example.com/schemas/schema.json",
    373   "type": "object",
    374   "properties": {
    375     "foo": { "$ref": "defs.json#/definitions/int" },
    376     "bar": { "$ref": "defs.json#/definitions/str" }
    377   }
    378 };
    379 
    380 var defsSchema = {
    381   "$id": "http://example.com/schemas/defs.json",
    382   "definitions": {
    383     "int": { "type": "integer" },
    384     "str": { "type": "string" }
    385   }
    386 };
    387 ```
    388 
    389 Now to compile your schema you can either pass all schemas to Ajv instance:
    390 
    391 ```javascript
    392 var ajv = new Ajv({schemas: [schema, defsSchema]});
    393 var validate = ajv.getSchema('http://example.com/schemas/schema.json');
    394 ```
    395 
    396 or use `addSchema` method:
    397 
    398 ```javascript
    399 var ajv = new Ajv;
    400 var validate = ajv.addSchema(defsSchema)
    401                   .compile(schema);
    402 ```
    403 
    404 See [Options](#options) and [addSchema](#api) method.
    405 
    406 __Please note__:
    407 - `$ref` is resolved as the uri-reference using schema $id as the base URI (see the example).
    408 - References can be recursive (and mutually recursive) to implement the schemas for different data structures (such as linked lists, trees, graphs, etc.).
    409 - You don't have to host your schema files at the URIs that you use as schema $id. These URIs are only used to identify the schemas, and according to JSON Schema specification validators should not expect to be able to download the schemas from these URIs.
    410 - The actual location of the schema file in the file system is not used.
    411 - You can pass the identifier of the schema as the second parameter of `addSchema` method or as a property name in `schemas` option. This identifier can be used instead of (or in addition to) schema $id.
    412 - You cannot have the same $id (or the schema identifier) used for more than one schema - the exception will be thrown.
    413 - You can implement dynamic resolution of the referenced schemas using `compileAsync` method. In this way you can store schemas in any system (files, web, database, etc.) and reference them without explicitly adding to Ajv instance. See [Asynchronous schema compilation](#asynchronous-schema-compilation).
    414 
    415 
    416 ## $data reference
    417 
    418 With `$data` option you can use values from the validated data as the values for the schema keywords. See [proposal](https://github.com/json-schema-org/json-schema-spec/issues/51) for more information about how it works.
    419 
    420 `$data` reference is supported in the keywords: const, enum, format, maximum/minimum, exclusiveMaximum / exclusiveMinimum, maxLength / minLength, maxItems / minItems, maxProperties / minProperties, formatMaximum / formatMinimum, formatExclusiveMaximum / formatExclusiveMinimum, multipleOf, pattern, required, uniqueItems.
    421 
    422 The value of "$data" should be a [JSON-pointer](https://tools.ietf.org/html/rfc6901) to the data (the root is always the top level data object, even if the $data reference is inside a referenced subschema) or a [relative JSON-pointer](http://tools.ietf.org/html/draft-luff-relative-json-pointer-00) (it is relative to the current point in data; if the $data reference is inside a referenced subschema it cannot point to the data outside of the root level for this subschema).
    423 
    424 Examples.
    425 
    426 This schema requires that the value in property `smaller` is less or equal than the value in the property larger:
    427 
    428 ```javascript
    429 var ajv = new Ajv({$data: true});
    430 
    431 var schema = {
    432   "properties": {
    433     "smaller": {
    434       "type": "number",
    435       "maximum": { "$data": "1/larger" }
    436     },
    437     "larger": { "type": "number" }
    438   }
    439 };
    440 
    441 var validData = {
    442   smaller: 5,
    443   larger: 7
    444 };
    445 
    446 ajv.validate(schema, validData); // true
    447 ```
    448 
    449 This schema requires that the properties have the same format as their field names:
    450 
    451 ```javascript
    452 var schema = {
    453   "additionalProperties": {
    454     "type": "string",
    455     "format": { "$data": "0#" }
    456   }
    457 };
    458 
    459 var validData = {
    460   'date-time': '1963-06-19T08:30:06.283185Z',
    461   email: 'joe.bloggs@example.com'
    462 }
    463 ```
    464 
    465 `$data` reference is resolved safely - it won't throw even if some property is undefined. If `$data` resolves to `undefined` the validation succeeds (with the exclusion of `const` keyword). If `$data` resolves to incorrect type (e.g. not "number" for maximum keyword) the validation fails.
    466 
    467 
    468 ## $merge and $patch keywords
    469 
    470 With the package [ajv-merge-patch](https://github.com/ajv-validator/ajv-merge-patch) you can use the keywords `$merge` and `$patch` that allow extending JSON Schemas with patches using formats [JSON Merge Patch (RFC 7396)](https://tools.ietf.org/html/rfc7396) and [JSON Patch (RFC 6902)](https://tools.ietf.org/html/rfc6902).
    471 
    472 To add keywords `$merge` and `$patch` to Ajv instance use this code:
    473 
    474 ```javascript
    475 require('ajv-merge-patch')(ajv);
    476 ```
    477 
    478 Examples.
    479 
    480 Using `$merge`:
    481 
    482 ```json
    483 {
    484   "$merge": {
    485     "source": {
    486       "type": "object",
    487       "properties": { "p": { "type": "string" } },
    488       "additionalProperties": false
    489     },
    490     "with": {
    491       "properties": { "q": { "type": "number" } }
    492     }
    493   }
    494 }
    495 ```
    496 
    497 Using `$patch`:
    498 
    499 ```json
    500 {
    501   "$patch": {
    502     "source": {
    503       "type": "object",
    504       "properties": { "p": { "type": "string" } },
    505       "additionalProperties": false
    506     },
    507     "with": [
    508       { "op": "add", "path": "/properties/q", "value": { "type": "number" } }
    509     ]
    510   }
    511 }
    512 ```
    513 
    514 The schemas above are equivalent to this schema:
    515 
    516 ```json
    517 {
    518   "type": "object",
    519   "properties": {
    520     "p": { "type": "string" },
    521     "q": { "type": "number" }
    522   },
    523   "additionalProperties": false
    524 }
    525 ```
    526 
    527 The properties `source` and `with` in the keywords `$merge` and `$patch` can use absolute or relative `$ref` to point to other schemas previously added to the Ajv instance or to the fragments of the current schema.
    528 
    529 See the package [ajv-merge-patch](https://github.com/ajv-validator/ajv-merge-patch) for more information.
    530 
    531 
    532 ## Defining custom keywords
    533 
    534 The advantages of using custom keywords are:
    535 
    536 - allow creating validation scenarios that cannot be expressed using JSON Schema
    537 - simplify your schemas
    538 - help bringing a bigger part of the validation logic to your schemas
    539 - make your schemas more expressive, less verbose and closer to your application domain
    540 - implement custom data processors that modify your data (`modifying` option MUST be used in keyword definition) and/or create side effects while the data is being validated
    541 
    542 If a keyword is used only for side-effects and its validation result is pre-defined, use option `valid: true/false` in keyword definition to simplify both generated code (no error handling in case of `valid: true`) and your keyword functions (no need to return any validation result).
    543 
    544 The concerns you have to be aware of when extending JSON Schema standard with custom keywords are the portability and understanding of your schemas. You will have to support these custom keywords on other platforms and to properly document these keywords so that everybody can understand them in your schemas.
    545 
    546 You can define custom keywords with [addKeyword](#api-addkeyword) method. Keywords are defined on the `ajv` instance level - new instances will not have previously defined keywords.
    547 
    548 Ajv allows defining keywords with:
    549 - validation function
    550 - compilation function
    551 - macro function
    552 - inline compilation function that should return code (as string) that will be inlined in the currently compiled schema.
    553 
    554 Example. `range` and `exclusiveRange` keywords using compiled schema:
    555 
    556 ```javascript
    557 ajv.addKeyword('range', {
    558   type: 'number',
    559   compile: function (sch, parentSchema) {
    560     var min = sch[0];
    561     var max = sch[1];
    562 
    563     return parentSchema.exclusiveRange === true
    564             ? function (data) { return data > min && data < max; }
    565             : function (data) { return data >= min && data <= max; }
    566   }
    567 });
    568 
    569 var schema = { "range": [2, 4], "exclusiveRange": true };
    570 var validate = ajv.compile(schema);
    571 console.log(validate(2.01)); // true
    572 console.log(validate(3.99)); // true
    573 console.log(validate(2)); // false
    574 console.log(validate(4)); // false
    575 ```
    576 
    577 Several custom keywords (typeof, instanceof, range and propertyNames) are defined in [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package - they can be used for your schemas and as a starting point for your own custom keywords.
    578 
    579 See [Defining custom keywords](https://github.com/ajv-validator/ajv/blob/master/CUSTOM.md) for more details.
    580 
    581 
    582 ## Asynchronous schema compilation
    583 
    584 During asynchronous compilation remote references are loaded using supplied function. See `compileAsync` [method](#api-compileAsync) and `loadSchema` [option](#options).
    585 
    586 Example:
    587 
    588 ```javascript
    589 var ajv = new Ajv({ loadSchema: loadSchema });
    590 
    591 ajv.compileAsync(schema).then(function (validate) {
    592   var valid = validate(data);
    593   // ...
    594 });
    595 
    596 function loadSchema(uri) {
    597   return request.json(uri).then(function (res) {
    598     if (res.statusCode >= 400)
    599       throw new Error('Loading error: ' + res.statusCode);
    600     return res.body;
    601   });
    602 }
    603 ```
    604 
    605 __Please note__: [Option](#options) `missingRefs` should NOT be set to `"ignore"` or `"fail"` for asynchronous compilation to work.
    606 
    607 
    608 ## Asynchronous validation
    609 
    610 Example in Node.js REPL: https://tonicdev.com/esp/ajv-asynchronous-validation
    611 
    612 You can define custom formats and keywords that perform validation asynchronously by accessing database or some other service. You should add `async: true` in the keyword or format definition (see [addFormat](#api-addformat), [addKeyword](#api-addkeyword) and [Defining custom keywords](#defining-custom-keywords)).
    613 
    614 If your schema uses asynchronous formats/keywords or refers to some schema that contains them it should have `"$async": true` keyword so that Ajv can compile it correctly. If asynchronous format/keyword or reference to asynchronous schema is used in the schema without `$async` keyword Ajv will throw an exception during schema compilation.
    615 
    616 __Please note__: all asynchronous subschemas that are referenced from the current or other schemas should have `"$async": true` keyword as well, otherwise the schema compilation will fail.
    617 
    618 Validation function for an asynchronous custom format/keyword should return a promise that resolves with `true` or `false` (or rejects with `new Ajv.ValidationError(errors)` if you want to return custom errors from the keyword function).
    619 
    620 Ajv compiles asynchronous schemas to [es7 async functions](http://tc39.github.io/ecmascript-asyncawait/) that can optionally be transpiled with [nodent](https://github.com/MatAtBread/nodent). Async functions are supported in Node.js 7+ and all modern browsers. You can also supply any other transpiler as a function via `processCode` option. See [Options](#options).
    621 
    622 The compiled validation function has `$async: true` property (if the schema is asynchronous), so you can differentiate these functions if you are using both synchronous and asynchronous schemas.
    623 
    624 Validation result will be a promise that resolves with validated data or rejects with an exception `Ajv.ValidationError` that contains the array of validation errors in `errors` property.
    625 
    626 
    627 Example:
    628 
    629 ```javascript
    630 var ajv = new Ajv;
    631 // require('ajv-async')(ajv);
    632 
    633 ajv.addKeyword('idExists', {
    634   async: true,
    635   type: 'number',
    636   validate: checkIdExists
    637 });
    638 
    639 
    640 function checkIdExists(schema, data) {
    641   return knex(schema.table)
    642   .select('id')
    643   .where('id', data)
    644   .then(function (rows) {
    645     return !!rows.length; // true if record is found
    646   });
    647 }
    648 
    649 var schema = {
    650   "$async": true,
    651   "properties": {
    652     "userId": {
    653       "type": "integer",
    654       "idExists": { "table": "users" }
    655     },
    656     "postId": {
    657       "type": "integer",
    658       "idExists": { "table": "posts" }
    659     }
    660   }
    661 };
    662 
    663 var validate = ajv.compile(schema);
    664 
    665 validate({ userId: 1, postId: 19 })
    666 .then(function (data) {
    667   console.log('Data is valid', data); // { userId: 1, postId: 19 }
    668 })
    669 .catch(function (err) {
    670   if (!(err instanceof Ajv.ValidationError)) throw err;
    671   // data is invalid
    672   console.log('Validation errors:', err.errors);
    673 });
    674 ```
    675 
    676 ### Using transpilers with asynchronous validation functions.
    677 
    678 [ajv-async](https://github.com/ajv-validator/ajv-async) uses [nodent](https://github.com/MatAtBread/nodent) to transpile async functions. To use another transpiler you should separately install it (or load its bundle in the browser).
    679 
    680 
    681 #### Using nodent
    682 
    683 ```javascript
    684 var ajv = new Ajv;
    685 require('ajv-async')(ajv);
    686 // in the browser if you want to load ajv-async bundle separately you can:
    687 // window.ajvAsync(ajv);
    688 var validate = ajv.compile(schema); // transpiled es7 async function
    689 validate(data).then(successFunc).catch(errorFunc);
    690 ```
    691 
    692 
    693 #### Using other transpilers
    694 
    695 ```javascript
    696 var ajv = new Ajv({ processCode: transpileFunc });
    697 var validate = ajv.compile(schema); // transpiled es7 async function
    698 validate(data).then(successFunc).catch(errorFunc);
    699 ```
    700 
    701 See [Options](#options).
    702 
    703 
    704 ## Security considerations
    705 
    706 JSON Schema, if properly used, can replace data sanitisation. It doesn't replace other API security considerations. It also introduces additional security aspects to consider.
    707 
    708 
    709 ##### Security contact
     177Learn how to use Ajv and see more examples in the [Guide: getting started](https://ajv.js.org/guide/getting-started.html)
     178
     179## Changes history
     180
     181See [https://github.com/ajv-validator/ajv/releases](https://github.com/ajv-validator/ajv/releases)
     182
     183**Please note**: [Changes in version 8.0.0](https://github.com/ajv-validator/ajv/releases/tag/v8.0.0)
     184
     185[Version 7.0.0](https://github.com/ajv-validator/ajv/releases/tag/v7.0.0)
     186
     187[Version 6.0.0](https://github.com/ajv-validator/ajv/releases/tag/v6.0.0).
     188
     189## Code of conduct
     190
     191Please review and follow the [Code of conduct](./CODE_OF_CONDUCT.md).
     192
     193Please report any unacceptable behaviour to ajv.validator@gmail.com - it will be reviewed by the project team.
     194
     195## Security contact
    710196
    711197To report a security vulnerability, please use the
    … …  
    713199Tidelift will coordinate the fix and disclosure. Please do NOT report security vulnerabilities via GitHub issues.
    714200
    715 
    716 ##### Untrusted schemas
    717 
    718 Ajv treats JSON schemas as trusted as your application code. This security model is based on the most common use case, when the schemas are static and bundled together with the application.
    719 
    720 If your schemas are received from untrusted sources (or generated from untrusted data) there are several scenarios you need to prevent:
    721 - compiling schemas can cause stack overflow (if they are too deep)
    722 - compiling schemas can be slow (e.g. [#557](https://github.com/ajv-validator/ajv/issues/557))
    723 - validating certain data can be slow
    724 
    725 It is difficult to predict all the scenarios, but at the very least it may help to limit the size of untrusted schemas (e.g. limit JSON string length) and also the maximum schema object depth (that can be high for relatively small JSON strings). You also may want to mitigate slow regular expressions in `pattern` and `patternProperties` keywords.
    726 
    727 Regardless the measures you take, using untrusted schemas increases security risks.
    728 
    729 
    730 ##### Circular references in JavaScript objects
    731 
    732 Ajv does not support schemas and validated data that have circular references in objects. See [issue #802](https://github.com/ajv-validator/ajv/issues/802).
    733 
    734 An attempt to compile such schemas or validate such data would cause stack overflow (or will not complete in case of asynchronous validation). Depending on the parser you use, untrusted data can lead to circular references.
    735 
    736 
    737 ##### Security risks of trusted schemas
    738 
    739 Some keywords in JSON Schemas can lead to very slow validation for certain data. These keywords include (but may be not limited to):
    740 
    741 - `pattern` and `format` for large strings - in some cases using `maxLength` can help mitigate it, but certain regular expressions can lead to exponential validation time even with relatively short strings (see [ReDoS attack](#redos-attack)).
    742 - `patternProperties` for large property names - use `propertyNames` to mitigate, but some regular expressions can have exponential evaluation time as well.
    743 - `uniqueItems` for large non-scalar arrays - use `maxItems` to mitigate
    744 
    745 __Please note__: The suggestions above to prevent slow validation would only work if you do NOT use `allErrors: true` in production code (using it would continue validation after validation errors).
    746 
    747 You can validate your JSON schemas against [this meta-schema](https://github.com/ajv-validator/ajv/blob/master/lib/refs/json-schema-secure.json) to check that these recommendations are followed:
    748 
    749 ```javascript
    750 const isSchemaSecure = ajv.compile(require('ajv/lib/refs/json-schema-secure.json'));
    751 
    752 const schema1 = {format: 'email'};
    753 isSchemaSecure(schema1); // false
    754 
    755 const schema2 = {format: 'email', maxLength: MAX_LENGTH};
    756 isSchemaSecure(schema2); // true
    757 ```
    758 
    759 __Please note__: following all these recommendation is not a guarantee that validation of untrusted data is safe - it can still lead to some undesirable results.
    760 
    761 
    762 ##### Content Security Policies (CSP)
    763 See [Ajv and Content Security Policies (CSP)](#ajv-and-content-security-policies-csp)
    764 
    765 
    766 ## ReDoS attack
    767 
    768 Certain regular expressions can lead to the exponential evaluation time even with relatively short strings.
    769 
    770 Please assess the regular expressions you use in the schemas on their vulnerability to this attack - see [safe-regex](https://github.com/substack/safe-regex), for example.
    771 
    772 __Please note__: some formats that Ajv implements use [regular expressions](https://github.com/ajv-validator/ajv/blob/master/lib/compile/formats.js) that can be vulnerable to ReDoS attack, so if you use Ajv to validate data from untrusted sources __it is strongly recommended__ to consider the following:
    773 
    774 - making assessment of "format" implementations in Ajv.
    775 - using `format: 'fast'` option that simplifies some of the regular expressions (although it does not guarantee that they are safe).
    776 - replacing format implementations provided by Ajv with your own implementations of "format" keyword that either uses different regular expressions or another approach to format validation. Please see [addFormat](#api-addformat) method.
    777 - disabling format validation by ignoring "format" keyword with option `format: false`
    778 
    779 Whatever mitigation you choose, please assume all formats provided by Ajv as potentially unsafe and make your own assessment of their suitability for your validation scenarios.
    780 
    781 
    782 ## Filtering data
    783 
    784 With [option `removeAdditional`](#options) (added by [andyscott](https://github.com/andyscott)) you can filter data during the validation.
    785 
    786 This option modifies original data.
    787 
    788 Example:
    789 
    790 ```javascript
    791 var ajv = new Ajv({ removeAdditional: true });
    792 var schema = {
    793   "additionalProperties": false,
    794   "properties": {
    795     "foo": { "type": "number" },
    796     "bar": {
    797       "additionalProperties": { "type": "number" },
    798       "properties": {
    799         "baz": { "type": "string" }
    800       }
    801     }
    802   }
    803 }
    804 
    805 var data = {
    806   "foo": 0,
    807   "additional1": 1, // will be removed; `additionalProperties` == false
    808   "bar": {
    809     "baz": "abc",
    810     "additional2": 2 // will NOT be removed; `additionalProperties` != false
    811   },
    812 }
    813 
    814 var validate = ajv.compile(schema);
    815 
    816 console.log(validate(data)); // true
    817 console.log(data); // { "foo": 0, "bar": { "baz": "abc", "additional2": 2 }
    818 ```
    819 
    820 If `removeAdditional` option in the example above were `"all"` then both `additional1` and `additional2` properties would have been removed.
    821 
    822 If the option were `"failing"` then property `additional1` would have been removed regardless of its value and property `additional2` would have been removed only if its value were failing the schema in the inner `additionalProperties` (so in the example above it would have stayed because it passes the schema, but any non-number would have been removed).
    823 
    824 __Please note__: If you use `removeAdditional` option with `additionalProperties` keyword inside `anyOf`/`oneOf` keywords your validation can fail with this schema, for example:
    825 
    826 ```json
    827 {
    828   "type": "object",
    829   "oneOf": [
    830     {
    831       "properties": {
    832         "foo": { "type": "string" }
    833       },
    834       "required": [ "foo" ],
    835       "additionalProperties": false
    836     },
    837     {
    838       "properties": {
    839         "bar": { "type": "integer" }
    840       },
    841       "required": [ "bar" ],
    842       "additionalProperties": false
    843     }
    844   ]
    845 }
    846 ```
    847 
    848 The intention of the schema above is to allow objects with either the string property "foo" or the integer property "bar", but not with both and not with any other properties.
    849 
    850 With the option `removeAdditional: true` the validation will pass for the object `{ "foo": "abc"}` but will fail for the object `{"bar": 1}`. It happens because while the first subschema in `oneOf` is validated, the property `bar` is removed because it is an additional property according to the standard (because it is not included in `properties` keyword in the same schema).
    851 
    852 While this behaviour is unexpected (issues [#129](https://github.com/ajv-validator/ajv/issues/129), [#134](https://github.com/ajv-validator/ajv/issues/134)), it is correct. To have the expected behaviour (both objects are allowed and additional properties are removed) the schema has to be refactored in this way:
    853 
    854 ```json
    855 {
    856   "type": "object",
    857   "properties": {
    858     "foo": { "type": "string" },
    859     "bar": { "type": "integer" }
    860   },
    861   "additionalProperties": false,
    862   "oneOf": [
    863     { "required": [ "foo" ] },
    864     { "required": [ "bar" ] }
    865   ]
    866 }
    867 ```
    868 
    869 The schema above is also more efficient - it will compile into a faster function.
    870 
    871 
    872 ## Assigning defaults
    873 
    874 With [option `useDefaults`](#options) Ajv will assign values from `default` keyword in the schemas of `properties` and `items` (when it is the array of schemas) to the missing properties and items.
    875 
    876 With the option value `"empty"` properties and items equal to `null` or `""` (empty string) will be considered missing and assigned defaults.
    877 
    878 This option modifies original data.
    879 
    880 __Please note__: the default value is inserted in the generated validation code as a literal, so the value inserted in the data will be the deep clone of the default in the schema.
    881 
    882 
    883 Example 1 (`default` in `properties`):
    884 
    885 ```javascript
    886 var ajv = new Ajv({ useDefaults: true });
    887 var schema = {
    888   "type": "object",
    889   "properties": {
    890     "foo": { "type": "number" },
    891     "bar": { "type": "string", "default": "baz" }
    892   },
    893   "required": [ "foo", "bar" ]
    894 };
    895 
    896 var data = { "foo": 1 };
    897 
    898 var validate = ajv.compile(schema);
    899 
    900 console.log(validate(data)); // true
    901 console.log(data); // { "foo": 1, "bar": "baz" }
    902 ```
    903 
    904 Example 2 (`default` in `items`):
    905 
    906 ```javascript
    907 var schema = {
    908   "type": "array",
    909   "items": [
    910     { "type": "number" },
    911     { "type": "string", "default": "foo" }
    912   ]
    913 }
    914 
    915 var data = [ 1 ];
    916 
    917 var validate = ajv.compile(schema);
    918 
    919 console.log(validate(data)); // true
    920 console.log(data); // [ 1, "foo" ]
    921 ```
    922 
    923 `default` keywords in other cases are ignored:
    924 
    925 - not in `properties` or `items` subschemas
    926 - in schemas inside `anyOf`, `oneOf` and `not` (see [#42](https://github.com/ajv-validator/ajv/issues/42))
    927 - in `if` subschema of `switch` keyword
    928 - in schemas generated by custom macro keywords
    929 
    930 The [`strictDefaults` option](#options) customizes Ajv's behavior for the defaults that Ajv ignores (`true` raises an error, and `"log"` outputs a warning).
    931 
    932 
    933 ## Coercing data types
    934 
    935 When you are validating user inputs all your data properties are usually strings. The option `coerceTypes` allows you to have your data types coerced to the types specified in your schema `type` keywords, both to pass the validation and to use the correctly typed data afterwards.
    936 
    937 This option modifies original data.
    938 
    939 __Please note__: if you pass a scalar value to the validating function its type will be coerced and it will pass the validation, but the value of the variable you pass won't be updated because scalars are passed by value.
    940 
    941 
    942 Example 1:
    943 
    944 ```javascript
    945 var ajv = new Ajv({ coerceTypes: true });
    946 var schema = {
    947   "type": "object",
    948   "properties": {
    949     "foo": { "type": "number" },
    950     "bar": { "type": "boolean" }
    951   },
    952   "required": [ "foo", "bar" ]
    953 };
    954 
    955 var data = { "foo": "1", "bar": "false" };
    956 
    957 var validate = ajv.compile(schema);
    958 
    959 console.log(validate(data)); // true
    960 console.log(data); // { "foo": 1, "bar": false }
    961 ```
    962 
    963 Example 2 (array coercions):
    964 
    965 ```javascript
    966 var ajv = new Ajv({ coerceTypes: 'array' });
    967 var schema = {
    968   "properties": {
    969     "foo": { "type": "array", "items": { "type": "number" } },
    970     "bar": { "type": "boolean" }
    971   }
    972 };
    973 
    974 var data = { "foo": "1", "bar": ["false"] };
    975 
    976 var validate = ajv.compile(schema);
    977 
    978 console.log(validate(data)); // true
    979 console.log(data); // { "foo": [1], "bar": false }
    980 ```
    981 
    982 The coercion rules, as you can see from the example, are different from JavaScript both to validate user input as expected and to have the coercion reversible (to correctly validate cases where different types are defined in subschemas of "anyOf" and other compound keywords).
    983 
    984 See [Coercion rules](https://github.com/ajv-validator/ajv/blob/master/COERCION.md) for details.
    985 
    986 
    987 ## API
    988 
    989 ##### new Ajv(Object options) -&gt; Object
    990 
    991 Create Ajv instance.
    992 
    993 
    994 ##### .compile(Object schema) -&gt; Function&lt;Object data&gt;
    995 
    996 Generate validating function and cache the compiled schema for future use.
    997 
    998 Validating function returns a boolean value. This function has properties `errors` and `schema`. Errors encountered during the last validation are assigned to `errors` property (it is assigned `null` if there was no errors). `schema` property contains the reference to the original schema.
    999 
    1000 The schema passed to this method will be validated against meta-schema unless `validateSchema` option is false. If schema is invalid, an error will be thrown. See [options](#options).
    1001 
    1002 
    1003 ##### <a name="api-compileAsync"></a>.compileAsync(Object schema [, Boolean meta] [, Function callback]) -&gt; Promise
    1004 
    1005 Asynchronous version of `compile` method that loads missing remote schemas using asynchronous function in `options.loadSchema`. This function returns a Promise that resolves to a validation function. An optional callback passed to `compileAsync` will be called with 2 parameters: error (or null) and validating function. The returned promise will reject (and the callback will be called with an error) when:
    1006 
    1007 - missing schema can't be loaded (`loadSchema` returns a Promise that rejects).
    1008 - a schema containing a missing reference is loaded, but the reference cannot be resolved.
    1009 - schema (or some loaded/referenced schema) is invalid.
    1010 
    1011 The function compiles schema and loads the first missing schema (or meta-schema) until all missing schemas are loaded.
    1012 
    1013 You can asynchronously compile meta-schema by passing `true` as the second parameter.
    1014 
    1015 See example in [Asynchronous compilation](#asynchronous-schema-compilation).
    1016 
    1017 
    1018 ##### .validate(Object schema|String key|String ref, data) -&gt; Boolean
    1019 
    1020 Validate data using passed schema (it will be compiled and cached).
    1021 
    1022 Instead of the schema you can use the key that was previously passed to `addSchema`, the schema id if it was present in the schema or any previously resolved reference.
    1023 
    1024 Validation errors will be available in the `errors` property of Ajv instance (`null` if there were no errors).
    1025 
    1026 __Please note__: every time this method is called the errors are overwritten so you need to copy them to another variable if you want to use them later.
    1027 
    1028 If the schema is asynchronous (has `$async` keyword on the top level) this method returns a Promise. See [Asynchronous validation](#asynchronous-validation).
    1029 
    1030 
    1031 ##### .addSchema(Array&lt;Object&gt;|Object schema [, String key]) -&gt; Ajv
    1032 
    1033 Add schema(s) to validator instance. This method does not compile schemas (but it still validates them). Because of that dependencies can be added in any order and circular dependencies are supported. It also prevents unnecessary compilation of schemas that are containers for other schemas but not used as a whole.
    1034 
    1035 Array of schemas can be passed (schemas should have ids), the second parameter will be ignored.
    1036 
    1037 Key can be passed that can be used to reference the schema and will be used as the schema id if there is no id inside the schema. If the key is not passed, the schema id will be used as the key.
    1038 
    1039 
    1040 Once the schema is added, it (and all the references inside it) can be referenced in other schemas and used to validate data.
    1041 
    1042 Although `addSchema` does not compile schemas, explicit compilation is not required - the schema will be compiled when it is used first time.
    1043 
    1044 By default the schema is validated against meta-schema before it is added, and if the schema does not pass validation the exception is thrown. This behaviour is controlled by `validateSchema` option.
    1045 
    1046 __Please note__: Ajv uses the [method chaining syntax](https://en.wikipedia.org/wiki/Method_chaining) for all methods with the prefix `add*` and `remove*`.
    1047 This allows you to do nice things like the following.
    1048 
    1049 ```javascript
    1050 var validate = new Ajv().addSchema(schema).addFormat(name, regex).getSchema(uri);
    1051 ```
    1052 
    1053 ##### .addMetaSchema(Array&lt;Object&gt;|Object schema [, String key]) -&gt; Ajv
    1054 
    1055 Adds meta schema(s) that can be used to validate other schemas. That function should be used instead of `addSchema` because there may be instance options that would compile a meta schema incorrectly (at the moment it is `removeAdditional` option).
    1056 
    1057 There is no need to explicitly add draft-07 meta schema (http://json-schema.org/draft-07/schema) - it is added by default, unless option `meta` is set to `false`. You only need to use it if you have a changed meta-schema that you want to use to validate your schemas. See `validateSchema`.
    1058 
    1059 
    1060 ##### <a name="api-validateschema"></a>.validateSchema(Object schema) -&gt; Boolean
    1061 
    1062 Validates schema. This method should be used to validate schemas rather than `validate` due to the inconsistency of `uri` format in JSON Schema standard.
    1063 
    1064 By default this method is called automatically when the schema is added, so you rarely need to use it directly.
    1065 
    1066 If schema doesn't have `$schema` property, it is validated against draft 6 meta-schema (option `meta` should not be false).
    1067 
    1068 If schema has `$schema` property, then the schema with this id (that should be previously added) is used to validate passed schema.
    1069 
    1070 Errors will be available at `ajv.errors`.
    1071 
    1072 
    1073 ##### .getSchema(String key) -&gt; Function&lt;Object data&gt;
    1074 
    1075 Retrieve compiled schema previously added with `addSchema` by the key passed to `addSchema` or by its full reference (id). The returned validating function has `schema` property with the reference to the original schema.
    1076 
    1077 
    1078 ##### .removeSchema([Object schema|String key|String ref|RegExp pattern]) -&gt; Ajv
    1079 
    1080 Remove added/cached schema. Even if schema is referenced by other schemas it can be safely removed as dependent schemas have local references.
    1081 
    1082 Schema can be removed using:
    1083 - key passed to `addSchema`
    1084 - it's full reference (id)
    1085 - RegExp that should match schema id or key (meta-schemas won't be removed)
    1086 - actual schema object that will be stable-stringified to remove schema from cache
    1087 
    1088 If no parameter is passed all schemas but meta-schemas will be removed and the cache will be cleared.
    1089 
    1090 
    1091 ##### <a name="api-addformat"></a>.addFormat(String name, String|RegExp|Function|Object format) -&gt; Ajv
    1092 
    1093 Add custom format to validate strings or numbers. It can also be used to replace pre-defined formats for Ajv instance.
    1094 
    1095 Strings are converted to RegExp.
    1096 
    1097 Function should return validation result as `true` or `false`.
    1098 
    1099 If object is passed it should have properties `validate`, `compare` and `async`:
    1100 
    1101 - _validate_: a string, RegExp or a function as described above.
    1102 - _compare_: an optional comparison function that accepts two strings and compares them according to the format meaning. This function is used with keywords `formatMaximum`/`formatMinimum` (defined in [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) package). It should return `1` if the first value is bigger than the second value, `-1` if it is smaller and `0` if it is equal.
    1103 - _async_: an optional `true` value if `validate` is an asynchronous function; in this case it should return a promise that resolves with a value `true` or `false`.
    1104 - _type_: an optional type of data that the format applies to. It can be `"string"` (default) or `"number"` (see https://github.com/ajv-validator/ajv/issues/291#issuecomment-259923858). If the type of data is different, the validation will pass.
    1105 
    1106 Custom formats can be also added via `formats` option.
    1107 
    1108 
    1109 ##### <a name="api-addkeyword"></a>.addKeyword(String keyword, Object definition) -&gt; Ajv
    1110 
    1111 Add custom validation keyword to Ajv instance.
    1112 
    1113 Keyword should be different from all standard JSON Schema keywords and different from previously defined keywords. There is no way to redefine keywords or to remove keyword definition from the instance.
    1114 
    1115 Keyword must start with a letter, `_` or `$`, and may continue with letters, numbers, `_`, `$`, or `-`.
    1116 It is recommended to use an application-specific prefix for keywords to avoid current and future name collisions.
    1117 
    1118 Example Keywords:
    1119 - `"xyz-example"`: valid, and uses prefix for the xyz project to avoid name collisions.
    1120 - `"example"`: valid, but not recommended as it could collide with future versions of JSON Schema etc.
    1121 - `"3-example"`: invalid as numbers are not allowed to be the first character in a keyword
    1122 
    1123 Keyword definition is an object with the following properties:
    1124 
    1125 - _type_: optional string or array of strings with data type(s) that the keyword applies to. If not present, the keyword will apply to all types.
    1126 - _validate_: validating function
    1127 - _compile_: compiling function
    1128 - _macro_: macro function
    1129 - _inline_: compiling function that returns code (as string)
    1130 - _schema_: an optional `false` value used with "validate" keyword to not pass schema
    1131 - _metaSchema_: an optional meta-schema for keyword schema
    1132 - _dependencies_: an optional list of properties that must be present in the parent schema - it will be checked during schema compilation
    1133 - _modifying_: `true` MUST be passed if keyword modifies data
    1134 - _statements_: `true` can be passed in case inline keyword generates statements (as opposed to expression)
    1135 - _valid_: pass `true`/`false` to pre-define validation result, the result returned from validation function will be ignored. This option cannot be used with macro keywords.
    1136 - _$data_: an optional `true` value to support [$data reference](#data-reference) as the value of custom keyword. The reference will be resolved at validation time. If the keyword has meta-schema it would be extended to allow $data and it will be used to validate the resolved value. Supporting $data reference requires that keyword has validating function (as the only option or in addition to compile, macro or inline function).
    1137 - _async_: an optional `true` value if the validation function is asynchronous (whether it is compiled or passed in _validate_ property); in this case it should return a promise that resolves with a value `true` or `false`. This option is ignored in case of "macro" and "inline" keywords.
    1138 - _errors_: an optional boolean or string `"full"` indicating whether keyword returns errors. If this property is not set Ajv will determine if the errors were set in case of failed validation.
    1139 
    1140 _compile_, _macro_ and _inline_ are mutually exclusive, only one should be used at a time. _validate_ can be used separately or in addition to them to support $data reference.
    1141 
    1142 __Please note__: If the keyword is validating data type that is different from the type(s) in its definition, the validation function will not be called (and expanded macro will not be used), so there is no need to check for data type inside validation function or inside schema returned by macro function (unless you want to enforce a specific type and for some reason do not want to use a separate `type` keyword for that). In the same way as standard keywords work, if the keyword does not apply to the data type being validated, the validation of this keyword will succeed.
    1143 
    1144 See [Defining custom keywords](#defining-custom-keywords) for more details.
    1145 
    1146 
    1147 ##### .getKeyword(String keyword) -&gt; Object|Boolean
    1148 
    1149 Returns custom keyword definition, `true` for pre-defined keywords and `false` if the keyword is unknown.
    1150 
    1151 
    1152 ##### .removeKeyword(String keyword) -&gt; Ajv
    1153 
    1154 Removes custom or pre-defined keyword so you can redefine them.
    1155 
    1156 While this method can be used to extend pre-defined keywords, it can also be used to completely change their meaning - it may lead to unexpected results.
    1157 
    1158 __Please note__: schemas compiled before the keyword is removed will continue to work without changes. To recompile schemas use `removeSchema` method and compile them again.
    1159 
    1160 
    1161 ##### .errorsText([Array&lt;Object&gt; errors [, Object options]]) -&gt; String
    1162 
    1163 Returns the text with all errors in a String.
    1164 
    1165 Options can have properties `separator` (string used to separate errors, ", " by default) and `dataVar` (the variable name that dataPaths are prefixed with, "data" by default).
    1166 
    1167 
    1168 ## Options
    1169 
    1170 Defaults:
    1171 
    1172 ```javascript
    1173 {
    1174   // validation and reporting options:
    1175   $data:            false,
    1176   allErrors:        false,
    1177   verbose:          false,
    1178   $comment:         false, // NEW in Ajv version 6.0
    1179   jsonPointers:     false,
    1180   uniqueItems:      true,
    1181   unicode:          true,
    1182   nullable:         false,
    1183   format:           'fast',
    1184   formats:          {},
    1185   unknownFormats:   true,
    1186   schemas:          {},
    1187   logger:           undefined,
    1188   // referenced schema options:
    1189   schemaId:         '$id',
    1190   missingRefs:      true,
    1191   extendRefs:       'ignore', // recommended 'fail'
    1192   loadSchema:       undefined, // function(uri: string): Promise {}
    1193   // options to modify validated data:
    1194   removeAdditional: false,
    1195   useDefaults:      false,
    1196   coerceTypes:      false,
    1197   // strict mode options
    1198   strictDefaults:   false,
    1199   strictKeywords:   false,
    1200   strictNumbers:    false,
    1201   // asynchronous validation options:
    1202   transpile:        undefined, // requires ajv-async package
    1203   // advanced options:
    1204   meta:             true,
    1205   validateSchema:   true,
    1206   addUsedSchema:    true,
    1207   inlineRefs:       true,
    1208   passContext:      false,
    1209   loopRequired:     Infinity,
    1210   ownProperties:    false,
    1211   multipleOfPrecision: false,
    1212   errorDataPath:    'object', // deprecated
    1213   messages:         true,
    1214   sourceCode:       false,
    1215   processCode:      undefined, // function (str: string, schema: object): string {}
    1216   cache:            new Cache,
    1217   serialize:        undefined
    1218 }
    1219 ```
    1220 
    1221 ##### Validation and reporting options
    1222 
    1223 - _$data_: support [$data references](#data-reference). Draft 6 meta-schema that is added by default will be extended to allow them. If you want to use another meta-schema you need to use $dataMetaSchema method to add support for $data reference. See [API](#api).
    1224 - _allErrors_: check all rules collecting all errors. Default is to return after the first error.
    1225 - _verbose_: include the reference to the part of the schema (`schema` and `parentSchema`) and validated data in errors (false by default).
    1226 - _$comment_ (NEW in Ajv version 6.0): log or pass the value of `$comment` keyword to a function. Option values:
    1227   - `false` (default): ignore $comment keyword.
    1228   - `true`: log the keyword value to console.
    1229   - function: pass the keyword value, its schema path and root schema to the specified function
    1230 - _jsonPointers_: set `dataPath` property of errors using [JSON Pointers](https://tools.ietf.org/html/rfc6901) instead of JavaScript property access notation.
    1231 - _uniqueItems_: validate `uniqueItems` keyword (true by default).
    1232 - _unicode_: calculate correct length of strings with unicode pairs (true by default). Pass `false` to use `.length` of strings that is faster, but gives "incorrect" lengths of strings with unicode pairs - each unicode pair is counted as two characters.
    1233 - _nullable_: support keyword "nullable" from [Open API 3 specification](https://swagger.io/docs/specification/data-models/data-types/).
    1234 - _format_: formats validation mode. Option values:
    1235   - `"fast"` (default) - simplified and fast validation (see [Formats](#formats) for details of which formats are available and affected by this option).
    1236   - `"full"` - more restrictive and slow validation. E.g., 25:00:00 and 2015/14/33 will be invalid time and date in 'full' mode but it will be valid in 'fast' mode.
    1237   - `false` - ignore all format keywords.
    1238 - _formats_: an object with custom formats. Keys and values will be passed to `addFormat` method.
    1239 - _keywords_: an object with custom keywords. Keys and values will be passed to `addKeyword` method.
    1240 - _unknownFormats_: handling of unknown formats. Option values:
    1241   - `true` (default) - if an unknown format is encountered the exception is thrown during schema compilation. If `format` keyword value is [$data reference](#data-reference) and it is unknown the validation will fail.
    1242   - `[String]` - an array of unknown format names that will be ignored. This option can be used to allow usage of third party schemas with format(s) for which you don't have definitions, but still fail if another unknown format is used. If `format` keyword value is [$data reference](#data-reference) and it is not in this array the validation will fail.
    1243   - `"ignore"` - to log warning during schema compilation and always pass validation (the default behaviour in versions before 5.0.0). This option is not recommended, as it allows to mistype format name and it won't be validated without any error message. This behaviour is required by JSON Schema specification.
    1244 - _schemas_: an array or object of schemas that will be added to the instance. In case you pass the array the schemas must have IDs in them. When the object is passed the method `addSchema(value, key)` will be called for each schema in this object.
    1245 - _logger_: sets the logging method. Default is the global `console` object that should have methods `log`, `warn` and `error`. See [Error logging](#error-logging). Option values:
    1246   - custom logger - it should have methods `log`, `warn` and `error`. If any of these methods is missing an exception will be thrown.
    1247   - `false` - logging is disabled.
    1248 
    1249 
    1250 ##### Referenced schema options
    1251 
    1252 - _schemaId_: this option defines which keywords are used as schema URI. Option value:
    1253   - `"$id"` (default) - only use `$id` keyword as schema URI (as specified in JSON Schema draft-06/07), ignore `id` keyword (if it is present a warning will be logged).
    1254   - `"id"` - only use `id` keyword as schema URI (as specified in JSON Schema draft-04), ignore `$id` keyword (if it is present a warning will be logged).
    1255   - `"auto"` - use both `$id` and `id` keywords as schema URI. If both are present (in the same schema object) and different the exception will be thrown during schema compilation.
    1256 - _missingRefs_: handling of missing referenced schemas. Option values:
    1257   - `true` (default) - if the reference cannot be resolved during compilation the exception is thrown. The thrown error has properties `missingRef` (with hash fragment) and `missingSchema` (without it). Both properties are resolved relative to the current base id (usually schema id, unless it was substituted).
    1258   - `"ignore"` - to log error during compilation and always pass validation.
    1259   - `"fail"` - to log error and successfully compile schema but fail validation if this rule is checked.
    1260 - _extendRefs_: validation of other keywords when `$ref` is present in the schema. Option values:
    1261   - `"ignore"` (default) - when `$ref` is used other keywords are ignored (as per [JSON Reference](https://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03#section-3) standard). A warning will be logged during the schema compilation.
    1262   - `"fail"` (recommended) - if other validation keywords are used together with `$ref` the exception will be thrown when the schema is compiled. This option is recommended to make sure schema has no keywords that are ignored, which can be confusing.
    1263   - `true` - validate all keywords in the schemas with `$ref` (the default behaviour in versions before 5.0.0).
    1264 - _loadSchema_: asynchronous function that will be used to load remote schemas when `compileAsync` [method](#api-compileAsync) is used and some reference is missing (option `missingRefs` should NOT be 'fail' or 'ignore'). This function should accept remote schema uri as a parameter and return a Promise that resolves to a schema. See example in [Asynchronous compilation](#asynchronous-schema-compilation).
    1265 
    1266 
    1267 ##### Options to modify validated data
    1268 
    1269 - _removeAdditional_: remove additional properties - see example in [Filtering data](#filtering-data). This option is not used if schema is added with `addMetaSchema` method. Option values:
    1270   - `false` (default) - not to remove additional properties
    1271   - `"all"` - all additional properties are removed, regardless of `additionalProperties` keyword in schema (and no validation is made for them).
    1272   - `true` - only additional properties with `additionalProperties` keyword equal to `false` are removed.
    1273   - `"failing"` - additional properties that fail schema validation will be removed (where `additionalProperties` keyword is `false` or schema).
    1274 - _useDefaults_: replace missing or undefined properties and items with the values from corresponding `default` keywords. Default behaviour is to ignore `default` keywords. This option is not used if schema is added with `addMetaSchema` method. See examples in [Assigning defaults](#assigning-defaults). Option values:
    1275   - `false` (default) - do not use defaults
    1276   - `true` - insert defaults by value (object literal is used).
    1277   - `"empty"` - in addition to missing or undefined, use defaults for properties and items that are equal to `null` or `""` (an empty string).
    1278   - `"shared"` (deprecated) - insert defaults by reference. If the default is an object, it will be shared by all instances of validated data. If you modify the inserted default in the validated data, it will be modified in the schema as well.
    1279 - _coerceTypes_: change data type of data to match `type` keyword. See the example in [Coercing data types](#coercing-data-types) and [coercion rules](https://github.com/ajv-validator/ajv/blob/master/COERCION.md). Option values:
    1280   - `false` (default) - no type coercion.
    1281   - `true` - coerce scalar data types.
    1282   - `"array"` - in addition to coercions between scalar types, coerce scalar data to an array with one element and vice versa (as required by the schema).
    1283 
    1284 
    1285 ##### Strict mode options
    1286 
    1287 - _strictDefaults_: report ignored `default` keywords in schemas. Option values:
    1288   - `false` (default) - ignored defaults are not reported
    1289   - `true` - if an ignored default is present, throw an error
    1290   - `"log"` - if an ignored default is present, log warning
    1291 - _strictKeywords_: report unknown keywords in schemas. Option values:
    1292   - `false` (default) - unknown keywords are not reported
    1293   - `true` - if an unknown keyword is present, throw an error
    1294   - `"log"` - if an unknown keyword is present, log warning
    1295 - _strictNumbers_: validate numbers strictly, failing validation for NaN and Infinity. Option values:
    1296   - `false` (default) - NaN or Infinity will pass validation for numeric types
    1297   - `true` - NaN or Infinity will not pass validation for numeric types
    1298 
    1299 ##### Asynchronous validation options
    1300 
    1301 - _transpile_: Requires [ajv-async](https://github.com/ajv-validator/ajv-async) package. It determines whether Ajv transpiles compiled asynchronous validation function. Option values:
    1302   - `undefined` (default) - transpile with [nodent](https://github.com/MatAtBread/nodent) if async functions are not supported.
    1303   - `true` - always transpile with nodent.
    1304   - `false` - do not transpile; if async functions are not supported an exception will be thrown.
    1305 
    1306 
    1307 ##### Advanced options
    1308 
    1309 - _meta_: add [meta-schema](http://json-schema.org/documentation.html) so it can be used by other schemas (true by default). If an object is passed, it will be used as the default meta-schema for schemas that have no `$schema` keyword. This default meta-schema MUST have `$schema` keyword.
    1310 - _validateSchema_: validate added/compiled schemas against meta-schema (true by default). `$schema` property in the schema can be http://json-schema.org/draft-07/schema or absent (draft-07 meta-schema will be used) or can be a reference to the schema previously added with `addMetaSchema` method. Option values:
    1311   - `true` (default) -  if the validation fails, throw the exception.
    1312   - `"log"` - if the validation fails, log error.
    1313   - `false` - skip schema validation.
    1314 - _addUsedSchema_: by default methods `compile` and `validate` add schemas to the instance if they have `$id` (or `id`) property that doesn't start with "#". If `$id` is present and it is not unique the exception will be thrown. Set this option to `false` to skip adding schemas to the instance and the `$id` uniqueness check when these methods are used. This option does not affect `addSchema` method.
    1315 - _inlineRefs_: Affects compilation of referenced schemas. Option values:
    1316   - `true` (default) - the referenced schemas that don't have refs in them are inlined, regardless of their size - that substantially improves performance at the cost of the bigger size of compiled schema functions.
    1317   - `false` - to not inline referenced schemas (they will be compiled as separate functions).
    1318   - integer number - to limit the maximum number of keywords of the schema that will be inlined.
    1319 - _passContext_: pass validation context to custom keyword functions. If this option is `true` and you pass some context to the compiled validation function with `validate.call(context, data)`, the `context` will be available as `this` in your custom keywords. By default `this` is Ajv instance.
    1320 - _loopRequired_: by default `required` keyword is compiled into a single expression (or a sequence of statements in `allErrors` mode). In case of a very large number of properties in this keyword it may result in a very big validation function. Pass integer to set the number of properties above which `required` keyword will be validated in a loop - smaller validation function size but also worse performance.
    1321 - _ownProperties_: by default Ajv iterates over all enumerable object properties; when this option is `true` only own enumerable object properties (i.e. found directly on the object rather than on its prototype) are iterated. Contributed by @mbroadst.
    1322 - _multipleOfPrecision_: by default `multipleOf` keyword is validated by comparing the result of division with parseInt() of that result. It works for dividers that are bigger than 1. For small dividers such as 0.01 the result of the division is usually not integer (even when it should be integer, see issue [#84](https://github.com/ajv-validator/ajv/issues/84)). If you need to use fractional dividers set this option to some positive integer N to have `multipleOf` validated using this formula: `Math.abs(Math.round(division) - division) < 1e-N` (it is slower but allows for float arithmetics deviations).
    1323 - _errorDataPath_ (deprecated): set `dataPath` to point to 'object' (default) or to 'property' when validating keywords `required`, `additionalProperties` and `dependencies`.
    1324 - _messages_: Include human-readable messages in errors. `true` by default. `false` can be passed when custom messages are used (e.g. with [ajv-i18n](https://github.com/ajv-validator/ajv-i18n)).
    1325 - _sourceCode_: add `sourceCode` property to validating function (for debugging; this code can be different from the result of toString call).
    1326 - _processCode_: an optional function to process generated code before it is passed to Function constructor. It can be used to either beautify (the validating function is generated without line-breaks) or to transpile code. Starting from version 5.0.0 this option replaced options:
    1327   - `beautify` that formatted the generated function using [js-beautify](https://github.com/beautify-web/js-beautify). If you want to beautify the generated code pass a function calling `require('js-beautify').js_beautify` as `processCode: code => js_beautify(code)`.
    1328   - `transpile` that transpiled asynchronous validation function. You can still use `transpile` option with [ajv-async](https://github.com/ajv-validator/ajv-async) package. See [Asynchronous validation](#asynchronous-validation) for more information.
    1329 - _cache_: an optional instance of cache to store compiled schemas using stable-stringified schema as a key. For example, set-associative cache [sacjs](https://github.com/epoberezkin/sacjs) can be used. If not passed then a simple hash is used which is good enough for the common use case (a limited number of statically defined schemas). Cache should have methods `put(key, value)`, `get(key)`, `del(key)` and `clear()`.
    1330 - _serialize_: an optional function to serialize schema to cache key. Pass `false` to use schema itself as a key (e.g., if WeakMap used as a cache). By default [fast-json-stable-stringify](https://github.com/epoberezkin/fast-json-stable-stringify) is used.
    1331 
    1332 
    1333 ## Validation errors
    1334 
    1335 In case of validation failure, Ajv assigns the array of errors to `errors` property of validation function (or to `errors` property of Ajv instance when `validate` or `validateSchema` methods were called). In case of [asynchronous validation](#asynchronous-validation), the returned promise is rejected with exception `Ajv.ValidationError` that has `errors` property.
    1336 
    1337 
    1338 ### Error objects
    1339 
    1340 Each error is an object with the following properties:
    1341 
    1342 - _keyword_: validation keyword.
    1343 - _dataPath_: the path to the part of the data that was validated. By default `dataPath` uses JavaScript property access notation (e.g., `".prop[1].subProp"`). When the option `jsonPointers` is true (see [Options](#options)) `dataPath` will be set using JSON pointer standard (e.g., `"/prop/1/subProp"`).
    1344 - _schemaPath_: the path (JSON-pointer as a URI fragment) to the schema of the keyword that failed validation.
    1345 - _params_: the object with the additional information about error that can be used to create custom error messages (e.g., using [ajv-i18n](https://github.com/ajv-validator/ajv-i18n) package). See below for parameters set by all keywords.
    1346 - _message_: the standard error message (can be excluded with option `messages` set to false).
    1347 - _schema_: the schema of the keyword (added with `verbose` option).
    1348 - _parentSchema_: the schema containing the keyword (added with `verbose` option)
    1349 - _data_: the data validated by the keyword (added with `verbose` option).
    1350 
    1351 __Please note__: `propertyNames` keyword schema validation errors have an additional property `propertyName`, `dataPath` points to the object. After schema validation for each property name, if it is invalid an additional error is added with the property `keyword` equal to `"propertyNames"`.
    1352 
    1353 
    1354 ### Error parameters
    1355 
    1356 Properties of `params` object in errors depend on the keyword that failed validation.
    1357 
    1358 - `maxItems`, `minItems`, `maxLength`, `minLength`, `maxProperties`, `minProperties` - property `limit` (number, the schema of the keyword).
    1359 - `additionalItems` - property `limit` (the maximum number of allowed items in case when `items` keyword is an array of schemas and `additionalItems` is false).
    1360 - `additionalProperties` - property `additionalProperty` (the property not used in `properties` and `patternProperties` keywords).
    1361 - `dependencies` - properties:
    1362   - `property` (dependent property),
    1363   - `missingProperty` (required missing dependency - only the first one is reported currently)
    1364   - `deps` (required dependencies, comma separated list as a string),
    1365   - `depsCount` (the number of required dependencies).
    1366 - `format` - property `format` (the schema of the keyword).
    1367 - `maximum`, `minimum` - properties:
    1368   - `limit` (number, the schema of the keyword),
    1369   - `exclusive` (boolean, the schema of `exclusiveMaximum` or `exclusiveMinimum`),
    1370   - `comparison` (string, comparison operation to compare the data to the limit, with the data on the left and the limit on the right; can be "<", "<=", ">", ">=")
    1371 - `multipleOf` - property `multipleOf` (the schema of the keyword)
    1372 - `pattern` - property `pattern` (the schema of the keyword)
    1373 - `required` - property `missingProperty` (required property that is missing).
    1374 - `propertyNames` - property `propertyName` (an invalid property name).
    1375 - `patternRequired` (in ajv-keywords) - property `missingPattern` (required pattern that did not match any property).
    1376 - `type` - property `type` (required type(s), a string, can be a comma-separated list)
    1377 - `uniqueItems` - properties `i` and `j` (indices of duplicate items).
    1378 - `const` - property `allowedValue` pointing to the value (the schema of the keyword).
    1379 - `enum` - property `allowedValues` pointing to the array of values (the schema of the keyword).
    1380 - `$ref` - property `ref` with the referenced schema URI.
    1381 - `oneOf` - property `passingSchemas` (array of indices of passing schemas, null if no schema passes).
    1382 - custom keywords (in case keyword definition doesn't create errors) - property `keyword` (the keyword name).
    1383 
    1384 
    1385 ### Error logging
    1386 
    1387 Using the `logger` option when initiallizing Ajv will allow you to define custom logging. Here you can build upon the exisiting logging. The use of other logging packages is supported as long as the package or its associated wrapper exposes the required methods. If any of the required methods are missing an exception will be thrown.
    1388 - **Required Methods**: `log`, `warn`, `error`
    1389 
    1390 ```javascript
    1391 var otherLogger = new OtherLogger();
    1392 var ajv = new Ajv({
    1393   logger: {
    1394     log: console.log.bind(console),
    1395     warn: function warn() {
    1396       otherLogger.logWarn.apply(otherLogger, arguments);
    1397     },
    1398     error: function error() {
    1399       otherLogger.logError.apply(otherLogger, arguments);
    1400       console.error.apply(console, arguments);
    1401     }
    1402   }
    1403 });
    1404 ```
    1405 
    1406 
    1407 ## Plugins
    1408 
    1409 Ajv can be extended with plugins that add custom keywords, formats or functions to process generated code. When such plugin is published as npm package it is recommended that it follows these conventions:
    1410 
    1411 - it exports a function
    1412 - this function accepts ajv instance as the first parameter and returns the same instance to allow chaining
    1413 - this function can accept an optional configuration as the second parameter
    1414 
    1415 If you have published a useful plugin please submit a PR to add it to the next section.
    1416 
    1417 
    1418 ## Related packages
    1419 
    1420 - [ajv-async](https://github.com/ajv-validator/ajv-async) - plugin to configure async validation mode
    1421 - [ajv-bsontype](https://github.com/BoLaMN/ajv-bsontype) - plugin to validate mongodb's bsonType formats
    1422 - [ajv-cli](https://github.com/jessedc/ajv-cli) - command line interface
    1423 - [ajv-errors](https://github.com/ajv-validator/ajv-errors) - plugin for custom error messages
    1424 - [ajv-i18n](https://github.com/ajv-validator/ajv-i18n) - internationalised error messages
    1425 - [ajv-istanbul](https://github.com/ajv-validator/ajv-istanbul) - plugin to instrument generated validation code to measure test coverage of your schemas
    1426 - [ajv-keywords](https://github.com/ajv-validator/ajv-keywords) - plugin with custom validation keywords (select, typeof, etc.)
    1427 - [ajv-merge-patch](https://github.com/ajv-validator/ajv-merge-patch) - plugin with keywords $merge and $patch
    1428 - [ajv-pack](https://github.com/ajv-validator/ajv-pack) - produces a compact module exporting validation functions
    1429 - [ajv-formats-draft2019](https://github.com/luzlab/ajv-formats-draft2019) - format validators for draft2019 that aren't already included in ajv (ie. `idn-hostname`, `idn-email`, `iri`, `iri-reference` and `duration`).
    1430 
    1431 ## Some packages using Ajv
    1432 
    1433 - [webpack](https://github.com/webpack/webpack) - a module bundler. Its main purpose is to bundle JavaScript files for usage in a browser
    1434 - [jsonscript-js](https://github.com/JSONScript/jsonscript-js) - the interpreter for [JSONScript](http://www.jsonscript.org) - scripted processing of existing endpoints and services
    1435 - [osprey-method-handler](https://github.com/mulesoft-labs/osprey-method-handler) - Express middleware for validating requests and responses based on a RAML method object, used in [osprey](https://github.com/mulesoft/osprey) - validating API proxy generated from a RAML definition
    1436 - [har-validator](https://github.com/ahmadnassri/har-validator) - HTTP Archive (HAR) validator
    1437 - [jsoneditor](https://github.com/josdejong/jsoneditor) - a web-based tool to view, edit, format, and validate JSON http://jsoneditoronline.org
    1438 - [JSON Schema Lint](https://github.com/nickcmaynard/jsonschemalint) - a web tool to validate JSON/YAML document against a single JSON Schema http://jsonschemalint.com
    1439 - [objection](https://github.com/vincit/objection.js) - SQL-friendly ORM for Node.js
    1440 - [table](https://github.com/gajus/table) - formats data into a string table
    1441 - [ripple-lib](https://github.com/ripple/ripple-lib) - a JavaScript API for interacting with [Ripple](https://ripple.com) in Node.js and the browser
    1442 - [restbase](https://github.com/wikimedia/restbase) - distributed storage with REST API & dispatcher for backend services built to provide a low-latency & high-throughput API for Wikipedia / Wikimedia content
    1443 - [hippie-swagger](https://github.com/CacheControl/hippie-swagger) - [Hippie](https://github.com/vesln/hippie) wrapper that provides end to end API testing with swagger validation
    1444 - [react-form-controlled](https://github.com/seeden/react-form-controlled) - React controlled form components with validation
    1445 - [rabbitmq-schema](https://github.com/tjmehta/rabbitmq-schema) - a schema definition module for RabbitMQ graphs and messages
    1446 - [@query/schema](https://www.npmjs.com/package/@query/schema) - stream filtering with a URI-safe query syntax parsing to JSON Schema
    1447 - [chai-ajv-json-schema](https://github.com/peon374/chai-ajv-json-schema) - chai plugin to us JSON Schema with expect in mocha tests
    1448 - [grunt-jsonschema-ajv](https://github.com/SignpostMarv/grunt-jsonschema-ajv) - Grunt plugin for validating files against JSON Schema
    1449 - [extract-text-webpack-plugin](https://github.com/webpack-contrib/extract-text-webpack-plugin) - extract text from bundle into a file
    1450 - [electron-builder](https://github.com/electron-userland/electron-builder) - a solution to package and build a ready for distribution Electron app
    1451 - [addons-linter](https://github.com/mozilla/addons-linter) - Mozilla Add-ons Linter
    1452 - [gh-pages-generator](https://github.com/epoberezkin/gh-pages-generator) - multi-page site generator converting markdown files to GitHub pages
    1453 - [ESLint](https://github.com/eslint/eslint) - the pluggable linting utility for JavaScript and JSX
    1454 
    1455 
    1456 ## Tests
    1457 
    1458 ```
    1459 npm install
    1460 git submodule update --init
    1461 npm test
    1462 ```
    1463 
    1464 ## Contributing
    1465 
    1466 All validation functions are generated using doT templates in [dot](https://github.com/ajv-validator/ajv/tree/master/lib/dot) folder. Templates are precompiled so doT is not a run-time dependency.
    1467 
    1468 `npm run build` - compiles templates to [dotjs](https://github.com/ajv-validator/ajv/tree/master/lib/dotjs) folder.
    1469 
    1470 `npm run watch` - automatically compiles templates when files in dot folder change
    1471 
    1472 Please see [Contributing guidelines](https://github.com/ajv-validator/ajv/blob/master/CONTRIBUTING.md)
    1473 
    1474 
    1475 ## Changes history
    1476 
    1477 See https://github.com/ajv-validator/ajv/releases
    1478 
    1479 __Please note__: [Changes in version 7.0.0-beta](https://github.com/ajv-validator/ajv/releases/tag/v7.0.0-beta.0)
    1480 
    1481 [Version 6.0.0](https://github.com/ajv-validator/ajv/releases/tag/v6.0.0).
    1482 
    1483 ## Code of conduct
    1484 
    1485 Please review and follow the [Code of conduct](https://github.com/ajv-validator/ajv/blob/master/CODE_OF_CONDUCT.md).
    1486 
    1487 Please report any unacceptable behaviour to ajv.validator@gmail.com - it will be reviewed by the project team.
    1488 
    1489 
    1490201## Open-source software support
    1491202
    1492203Ajv is a part of [Tidelift subscription](https://tidelift.com/subscription/pkg/npm-ajv?utm_source=npm-ajv&utm_medium=referral&utm_campaign=readme) - it provides a centralised support to open-source software users, in addition to the support provided by software maintainers.
    1493204
    1494 
    1495205## License
    1496206
    1497 [MIT](https://github.com/ajv-validator/ajv/blob/master/LICENSE)
     207[MIT](./LICENSE)
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