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- # 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)
-
- > Map `visit` over an array of objects.
-
- ## Install
-
- Install with [npm](https://www.npmjs.com/):
-
- ```sh
- $ npm install --save map-visit
- ```
-
- ## Usage
-
- ```js
- var mapVisit = require('map-visit');
- ```
-
- ## What does this do?
-
- **Assign/Merge/Extend vs. Visit**
-
- Let's say you want to add a `set` method to your application that will:
-
- * set key-value pairs on a `data` object
- * extend objects onto the `data` object
- * extend arrays of objects onto the data object
-
- **Example using `extend`**
-
- Here is one way to accomplish this using Lo-Dash's `extend` (comparable to `Object.assign`):
-
- ```js
- var _ = require('lodash');
-
- var obj = {
- data: {},
- set: function (key, value) {
- if (Array.isArray(key)) {
- _.extend.apply(_, [obj.data].concat(key));
- } else if (typeof key === 'object') {
- _.extend(obj.data, key);
- } else {
- obj.data[key] = value;
- }
- }
- };
-
- obj.set('a', 'a');
- obj.set([{b: 'b'}, {c: 'c'}]);
- obj.set({d: {e: 'f'}});
-
- console.log(obj.data);
- //=> {a: 'a', b: 'b', c: 'c', d: { e: 'f' }}
- ```
-
- 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`.
-
- **Example using `visit`**
-
- In this approach:
-
- * when an array is passed to `set`, the `mapVisit` library calls the `set` method on each object in the array.
- * when an object is passed, `visit` calls `set` on each property in the object.
-
- 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).
-
- ```js
- var mapVisit = require('map-visit');
- var visit = require('object-visit');
-
- var obj = {
- data: {},
- set: function (key, value) {
- if (Array.isArray(key)) {
- mapVisit(obj, 'set', key);
- } else if (typeof key === 'object') {
- visit(obj, 'set', key);
- } else {
- // simulate an event-emitter
- console.log('emit', key, value);
- obj.data[key] = value;
- }
- }
- };
-
- obj.set('a', 'a');
- obj.set([{b: 'b'}, {c: 'c'}]);
- obj.set({d: {e: 'f'}});
- obj.set({g: 'h', i: 'j', k: 'l'});
-
- console.log(obj.data);
- //=> {a: 'a', b: 'b', c: 'c', d: { e: 'f' }, g: 'h', i: 'j', k: 'l'}
-
- // events would look something like:
- // emit a a
- // emit b b
- // emit c c
- // emit d { e: 'f' }
- // emit g h
- // emit i j
- // emit k l
- ```
-
- ## About
-
- ### Related projects
-
- * [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.")
- * [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.")
-
- ### Contributing
-
- Pull requests and stars are always welcome. For bugs and feature requests, [please create an issue](../../issues/new).
-
- ### Contributors
-
- | **Commits** | **Contributor** |
- | --- | --- |
- | 15 | [jonschlinkert](https://github.com/jonschlinkert) |
- | 7 | [doowb](https://github.com/doowb) |
-
- ### Building docs
-
- _(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.)_
-
- To generate the readme, run the following command:
-
- ```sh
- $ npm install -g verbose/verb#dev verb-generate-readme && verb
- ```
-
- ### Running tests
-
- 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:
-
- ```sh
- $ npm install && npm test
- ```
-
- ### Author
-
- **Jon Schlinkert**
-
- * [github/jonschlinkert](https://github.com/jonschlinkert)
- * [twitter/jonschlinkert](https://twitter.com/jonschlinkert)
-
- ### License
-
- Copyright © 2017, [Jon Schlinkert](https://github.com/jonschlinkert).
- Released under the [MIT License](LICENSE).
-
- ***
-
- _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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