map-visit

What is map-visit?

The map-visit npm package is designed to map over the properties of an object and apply a function to each property's value. It is particularly useful for manipulating and transforming object properties in a flexible and customizable way.

What are map-visit's main functionalities?

Mapping over object properties

This feature allows you to iterate over each property of an object and apply a function to its value. In the provided code sample, the function converts each property value to uppercase and logs it along with its key.

const mapVisit = require('map-visit');
const obj = { a: 'foo', b: 'bar' };
mapVisit(obj, (value, key) => console.log(key, value.toUpperCase()));

Other packages similar to map-visit

object-map

Similar to map-visit, object-map allows mapping over an object's properties to transform their values. However, object-map returns a new object with the transformed properties, whereas map-visit applies a function for side effects without necessarily returning a result.

map-obj

map-obj is another package that provides functionality to map keys and values of an object. Unlike map-visit, which is used for applying functions to object properties primarily for side effects, map-obj focuses on transforming the keys and values and returning a new object, which can be useful for more functional programming approaches.

README

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.

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