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1# map-visit [![NPM version](https://img.shields.io/npm/v/map-visit.svg?style=flat)](https://www.npmjs.com/package/map-visit) [![NPM monthly downloads](https://img.shields.io/npm/dm/map-visit.svg?style=flat)](https://npmjs.org/package/map-visit) [![NPM total downloads](https://img.shields.io/npm/dt/map-visit.svg?style=flat)](https://npmjs.org/package/map-visit) [![Linux Build Status](https://img.shields.io/travis/jonschlinkert/map-visit.svg?style=flat&label=Travis)](https://travis-ci.org/jonschlinkert/map-visit)
2
3> Map `visit` over an array of objects.
4
5## Install
6
7Install with [npm](https://www.npmjs.com/):
8
9```sh
10$ npm install --save map-visit
11```
12
13## Usage
14
15```js
16var mapVisit = require('map-visit');
17```
18
19## What does this do?
20
21**Assign/Merge/Extend vs. Visit**
22
23Let's say you want to add a `set` method to your application that will:
24
25* set key-value pairs on a `data` object
26* extend objects onto the `data` object
27* extend arrays of objects onto the data object
28
29**Example using `extend`**
30
31Here is one way to accomplish this using Lo-Dash's `extend` (comparable to `Object.assign`):
32
33```js
34var _ = require('lodash');
35
36var obj = {
37 data: {},
38 set: function (key, value) {
39 if (Array.isArray(key)) {
40 _.extend.apply(_, [obj.data].concat(key));
41 } else if (typeof key === 'object') {
42 _.extend(obj.data, key);
43 } else {
44 obj.data[key] = value;
45 }
46 }
47};
48
49obj.set('a', 'a');
50obj.set([{b: 'b'}, {c: 'c'}]);
51obj.set({d: {e: 'f'}});
52
53console.log(obj.data);
54//=> {a: 'a', b: 'b', c: 'c', d: { e: 'f' }}
55```
56
57The above approach works fine for most use cases. However, **if you also want to emit an event** each time a property is added to the `data` object, or you want more control over what happens as the object is extended, a better approach would be to use `visit`.
58
59**Example using `visit`**
60
61In this approach:
62
63* when an array is passed to `set`, the `mapVisit` library calls the `set` method on each object in the array.
64* when an object is passed, `visit` calls `set` on each property in the object.
65
66As a result, the `data` event will be emitted every time a property is added to `data` (events are just an example, you can use this approach to perform any necessary logic every time the method is called).
67
68```js
69var mapVisit = require('map-visit');
70var visit = require('object-visit');
71
72var obj = {
73 data: {},
74 set: function (key, value) {
75 if (Array.isArray(key)) {
76 mapVisit(obj, 'set', key);
77 } else if (typeof key === 'object') {
78 visit(obj, 'set', key);
79 } else {
80 // simulate an event-emitter
81 console.log('emit', key, value);
82 obj.data[key] = value;
83 }
84 }
85};
86
87obj.set('a', 'a');
88obj.set([{b: 'b'}, {c: 'c'}]);
89obj.set({d: {e: 'f'}});
90obj.set({g: 'h', i: 'j', k: 'l'});
91
92console.log(obj.data);
93//=> {a: 'a', b: 'b', c: 'c', d: { e: 'f' }, g: 'h', i: 'j', k: 'l'}
94
95// events would look something like:
96// emit a a
97// emit b b
98// emit c c
99// emit d { e: 'f' }
100// emit g h
101// emit i j
102// emit k l
103```
104
105## About
106
107### Related projects
108
109* [collection-visit](https://www.npmjs.com/package/collection-visit): Visit a method over the items in an object, or map visit over the objects… [more](https://github.com/jonschlinkert/collection-visit) | [homepage](https://github.com/jonschlinkert/collection-visit "Visit a method over the items in an object, or map visit over the objects in an array.")
110* [object-visit](https://www.npmjs.com/package/object-visit): Call a specified method on each value in the given object. | [homepage](https://github.com/jonschlinkert/object-visit "Call a specified method on each value in the given object.")
111
112### Contributing
113
114Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
115
116### Contributors
117
118| **Commits** | **Contributor** |
119| --- | --- |
120| 15 | [jonschlinkert](https://github.com/jonschlinkert) |
121| 7 | [doowb](https://github.com/doowb) |
122
123### Building docs
124
125_(This project's readme.md is generated by [verb](https://github.com/verbose/verb-generate-readme), please don't edit the readme directly. Any changes to the readme must be made in the [.verb.md](.verb.md) readme template.)_
126
127To generate the readme, run the following command:
128
129```sh
130$ npm install -g verbose/verb#dev verb-generate-readme && verb
131```
132
133### Running tests
134
135Running and reviewing unit tests is a great way to get familiarized with a library and its API. You can install dependencies and run tests with the following command:
136
137```sh
138$ npm install && npm test
139```
140
141### Author
142
143**Jon Schlinkert**
144
145* [github/jonschlinkert](https://github.com/jonschlinkert)
146* [twitter/jonschlinkert](https://twitter.com/jonschlinkert)
147
148### License
149
150Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert).
151Released under the [MIT License](LICENSE).
152
153***
154
155_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.5.0, on April 09, 2017._
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