lodash.keyby

What is lodash.keyby?

The lodash.keyby package is a utility function from the Lodash library that creates an object composed of keys generated from the results of running each element of a collection through an iteratee function. The corresponding value of each key is the last element responsible for generating the key.

What are lodash.keyby's main functionalities?

Basic Usage

This feature demonstrates the basic usage of lodash.keyby where an array of objects is transformed into an object keyed by the specified property ('dir' in this case).

const _ = require('lodash.keyby');
const array = [
  { 'dir': 'left', 'code': 97 },
  { 'dir': 'right', 'code': 100 }
];
const result = _.keyBy(array, 'dir');
console.log(result); // { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }

Using a Function as Iteratee

This feature shows how to use a function as the iteratee to generate the keys. In this example, the objects are keyed by their 'type' property.

const _ = require('lodash.keyby');
const array = [
  { 'name': 'apple', 'type': 'fruit' },
  { 'name': 'carrot', 'type': 'vegetable' }
];
const result = _.keyBy(array, function(o) { return o.type; });
console.log(result); // { 'fruit': { 'name': 'apple', 'type': 'fruit' }, 'vegetable': { 'name': 'carrot', 'type': 'vegetable' } }

Handling Duplicate Keys

This feature demonstrates how lodash.keyby handles duplicate keys. The last element with the duplicate key will overwrite the previous ones.

const _ = require('lodash.keyby');
const array = [
  { 'name': 'apple', 'type': 'fruit' },
  { 'name': 'banana', 'type': 'fruit' }
];
const result = _.keyBy(array, 'type');
console.log(result); // { 'fruit': { 'name': 'banana', 'type': 'fruit' } }

Other packages similar to lodash.keyby

ramda

Ramda is a functional programming library for JavaScript. It provides a similar function called R.indexBy, which works similarly to lodash.keyby by creating an object indexed by a specified key. Ramda emphasizes immutability and side-effect-free functions, making it a good choice for functional programming paradigms.

underscore

Underscore is a JavaScript library that provides utility functions for common programming tasks. It includes a function called _.indexBy, which is similar to lodash.keyby. Underscore is known for its simplicity and ease of use, though it is less feature-rich compared to Lodash.

README

lodash.keyby v4.6.0

The lodash method _.keyBy exported as a Node.js module.

Installation

Using npm:

$ {sudo -H} npm i -g npm
$ npm i --save lodash.keyby

In Node.js:

var keyBy = require('lodash.keyby');

See the documentation or package source for more details.