source: trip-planner-front/node_modules/regexpu-core/README.md

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1# regexpu-core [![Build status](https://github.com/mathiasbynens/regexpu-core/workflows/run-checks/badge.svg)](https://github.com/mathiasbynens/regexpu-core/actions?query=workflow%3Arun-checks) [![regexpu-core on npm](https://img.shields.io/npm/v/regexpu-core)](https://www.npmjs.com/package/regexpu-core)
2
3_regexpu_ is a source code transpiler that enables the use of ES2015 Unicode regular expressions in JavaScript-of-today (ES5).
4
5_regexpu-core_ contains _regexpu_’s core functionality, i.e. `rewritePattern(pattern, flag)`, which enables rewriting regular expressions that make use of [the ES2015 `u` flag](https://mathiasbynens.be/notes/es6-unicode-regex) into equivalent ES5-compatible regular expression patterns.
6
7## Installation
8
9To use _regexpu-core_ programmatically, install it as a dependency via [npm](https://www.npmjs.com/):
10
11```bash
12npm install regexpu-core --save
13```
14
15Then, `require` it:
16
17```js
18const rewritePattern = require('regexpu-core');
19```
20
21## API
22
23This module exports a single function named `rewritePattern`.
24
25### `rewritePattern(pattern, flags, options)`
26
27This function takes a string that represents a regular expression pattern as well as a string representing its flags, and returns an ES5-compatible version of the pattern.
28
29```js
30rewritePattern('foo.bar', 'u');
31// → 'foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uD7FF\\uDC00-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF])bar'
32
33rewritePattern('[\\u{1D306}-\\u{1D308}a-z]', 'u');
34// → '(?:[a-z]|\\uD834[\\uDF06-\\uDF08])'
35
36rewritePattern('[\\u{1D306}-\\u{1D308}a-z]', 'ui');
37// → '(?:[a-z\\u017F\\u212A]|\\uD834[\\uDF06-\\uDF08])'
38```
39
40_regexpu-core_ can rewrite non-ES6 regular expressions too, which is useful to demonstrate how their behavior changes once the `u` and `i` flags are added:
41
42```js
43// In ES5, the dot operator only matches BMP symbols:
44rewritePattern('foo.bar');
45// → 'foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF])bar'
46
47// But with the ES2015 `u` flag, it matches astral symbols too:
48rewritePattern('foo.bar', 'u');
49// → 'foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uD7FF\\uDC00-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF])bar'
50```
51
52The optional `options` argument recognizes the following properties:
53
54#### `dotAllFlag` (default: `false`)
55
56Setting this option to `true` enables support for [the `s` (`dotAll`) flag](https://github.com/mathiasbynens/es-regexp-dotall-flag).
57
58```js
59rewritePattern('.');
60// → '[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF]'
61
62rewritePattern('.', '', {
63 'dotAllFlag': true
64});
65// → '[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF]'
66
67rewritePattern('.', 's', {
68 'dotAllFlag': true
69});
70// → '[\\0-\\uFFFF]'
71
72rewritePattern('.', 'su', {
73 'dotAllFlag': true
74});
75// → '(?:[\\0-\\uD7FF\\uE000-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF](?![\\uDC00-\\uDFFF])|(?:[^\\uD800-\\uDBFF]|^)[\\uDC00-\\uDFFF])'
76```
77
78#### `unicodePropertyEscape` (default: `false`)
79
80Setting this option to `true` enables [support for Unicode property escapes](property-escapes.md):
81
82```js
83rewritePattern('\\p{Script_Extensions=Anatolian_Hieroglyphs}', 'u', {
84 'unicodePropertyEscape': true
85});
86// → '(?:\\uD811[\\uDC00-\\uDE46])'
87```
88
89#### `lookbehind` (default: `false`)
90
91Setting this option to `true` enables support for [lookbehind assertions](https://github.com/tc39/proposal-regexp-lookbehind).
92
93```js
94rewritePattern('(?<=.)a', '', {
95 'lookbehind': true
96});
97// → '(?<=[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF])a'
98```
99
100#### `namedGroup` (default: `false`)
101
102Setting this option to `true` enables support for [named capture groups](https://github.com/tc39/proposal-regexp-named-groups).
103
104```js
105rewritePattern('(?<name>.)\k<name>', '', {
106 'namedGroup': true
107});
108// → '(.)\1'
109```
110
111#### `onNamedGroup`
112
113This option is a function that gets called when a named capture group is found. It receives two parameters:
114the name of the group, and its index.
115
116```js
117rewritePattern('(?<name>.)\k<name>', '', {
118 'namedGroup': true,
119 onNamedGroup(name, index) {
120 console.log(name, index);
121 // → 'name', 1
122 }
123});
124```
125
126#### `useUnicodeFlag` (default: `false`)
127
128Setting this option to `true` enables the use of Unicode code point escapes of the form `\u{…}`. Note that in regular expressions, such escape sequences only work correctly when the ES2015 `u` flag is set. Enabling this setting often results in more compact output, although there are cases (such as `\p{Lu}`) where it actually _increases_ the output size.
129
130```js
131rewritePattern('\\p{Script_Extensions=Anatolian_Hieroglyphs}', 'u', {
132 'unicodePropertyEscape': true,
133 'useUnicodeFlag': true
134});
135// → '[\\u{14400}-\\u{14646}]'
136```
137
138## For maintainers
139
140### How to publish a new release
141
1421. On the `main` branch, bump the version number in `package.json`:
143
144 ```sh
145 npm version patch -m 'Release v%s'
146 ```
147
148 Instead of `patch`, use `minor` or `major` [as needed](https://semver.org/).
149
150 Note that this produces a Git commit + tag.
151
1521. Push the release commit and tag:
153
154 ```sh
155 git push && git push --tags
156 ```
157
158 Our CI then automatically publishes the new release to npm.
159
160## Author
161
162| [![twitter/mathias](https://gravatar.com/avatar/24e08a9ea84deb17ae121074d0f17125?s=70)](https://twitter.com/mathias "Follow @mathias on Twitter") |
163|---|
164| [Mathias Bynens](https://mathiasbynens.be/) |
165
166## License
167
168_regexpu-core_ is available under the [MIT](https://mths.be/mit) license.
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