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map-visit

> Map `visit` over an array of objects.

# Install

Install with npm:

$ npm install --save map-visit

# Usage

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`):

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).

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: Visit a method over the items in an object, or map visit over the objects… more | homepage
- object-visit: Call a specified method on each value in the given object. | homepage

## Contributing

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.

## Contributors

Commits | Contributor
--- | ---
15 | jonschlinkert
7 | doowb

## Building docs

_(This project's readme.md is generated by verb, please don't edit the readme directly. Any changes to the readme must be made in the .verb.md readme template.)_

To generate the readme, run the following command:

$ 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:

$ npm install && npm test

## Author

Jon Schlinkert

- github/jonschlinkert
- twitter/jonschlinkert

## License

Copyright © 2017, Jon Schlinkert. Released under the [MIT License](LICENSE).

This file was generated by verb-generate-readme, v0.5.0, on April 09, 2017.