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)
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2 |
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3 | > Map `visit` over an array of objects.
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4 |
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5 | ## Install
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6 |
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7 | Install with [npm](https://www.npmjs.com/):
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8 |
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9 | ```sh
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10 | $ npm install --save map-visit
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11 | ```
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12 |
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13 | ## Usage
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14 |
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15 | ```js
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16 | var mapVisit = require('map-visit');
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17 | ```
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18 |
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19 | ## What does this do?
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20 |
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21 | **Assign/Merge/Extend vs. Visit**
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22 |
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23 | Let's say you want to add a `set` method to your application that will:
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24 |
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25 | * set key-value pairs on a `data` object
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26 | * extend objects onto the `data` object
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27 | * extend arrays of objects onto the data object
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28 |
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29 | **Example using `extend`**
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30 |
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31 | Here is one way to accomplish this using Lo-Dash's `extend` (comparable to `Object.assign`):
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32 |
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33 | ```js
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34 | var _ = require('lodash');
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35 |
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36 | var obj = {
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37 | data: {},
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38 | set: function (key, value) {
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39 | if (Array.isArray(key)) {
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40 | _.extend.apply(_, [obj.data].concat(key));
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41 | } else if (typeof key === 'object') {
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42 | _.extend(obj.data, key);
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43 | } else {
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44 | obj.data[key] = value;
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45 | }
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46 | }
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47 | };
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48 |
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49 | obj.set('a', 'a');
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50 | obj.set([{b: 'b'}, {c: 'c'}]);
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51 | obj.set({d: {e: 'f'}});
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52 |
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53 | console.log(obj.data);
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54 | //=> {a: 'a', b: 'b', c: 'c', d: { e: 'f' }}
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55 | ```
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56 |
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57 | The 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`.
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58 |
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59 | **Example using `visit`**
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60 |
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61 | In this approach:
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62 |
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63 | * when an array is passed to `set`, the `mapVisit` library calls the `set` method on each object in the array.
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64 | * when an object is passed, `visit` calls `set` on each property in the object.
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65 |
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66 | As 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).
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67 |
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68 | ```js
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69 | var mapVisit = require('map-visit');
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70 | var visit = require('object-visit');
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71 |
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72 | var obj = {
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73 | data: {},
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74 | set: function (key, value) {
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75 | if (Array.isArray(key)) {
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76 | mapVisit(obj, 'set', key);
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77 | } else if (typeof key === 'object') {
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78 | visit(obj, 'set', key);
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79 | } else {
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80 | // simulate an event-emitter
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81 | console.log('emit', key, value);
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82 | obj.data[key] = value;
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83 | }
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84 | }
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85 | };
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86 |
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87 | obj.set('a', 'a');
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88 | obj.set([{b: 'b'}, {c: 'c'}]);
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89 | obj.set({d: {e: 'f'}});
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90 | obj.set({g: 'h', i: 'j', k: 'l'});
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91 |
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92 | console.log(obj.data);
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93 | //=> {a: 'a', b: 'b', c: 'c', d: { e: 'f' }, g: 'h', i: 'j', k: 'l'}
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94 |
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95 | // events would look something like:
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96 | // emit a a
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97 | // emit b b
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98 | // emit c c
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99 | // emit d { e: 'f' }
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100 | // emit g h
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101 | // emit i j
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102 | // emit k l
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103 | ```
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104 |
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105 | ## About
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106 |
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107 | ### Related projects
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108 |
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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.")
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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.")
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111 |
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112 | ### Contributing
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113 |
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114 | Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
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115 |
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116 | ### Contributors
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117 |
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118 | | **Commits** | **Contributor** |
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119 | | --- | --- |
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120 | | 15 | [jonschlinkert](https://github.com/jonschlinkert) |
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121 | | 7 | [doowb](https://github.com/doowb) |
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122 |
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123 | ### Building docs
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124 |
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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.)_
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126 |
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127 | To generate the readme, run the following command:
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128 |
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129 | ```sh
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130 | $ npm install -g verbose/verb#dev verb-generate-readme && verb
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131 | ```
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132 |
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133 | ### Running tests
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134 |
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135 | Running 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:
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136 |
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137 | ```sh
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138 | $ npm install && npm test
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139 | ```
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140 |
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141 | ### Author
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142 |
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143 | **Jon Schlinkert**
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144 |
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145 | * [github/jonschlinkert](https://github.com/jonschlinkert)
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146 | * [twitter/jonschlinkert](https://twitter.com/jonschlinkert)
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147 |
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148 | ### License
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149 |
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150 | Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert).
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151 | Released under the [MIT License](LICENSE).
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152 |
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153 | ***
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154 |
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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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