Lodash _.keyBy() Method

Lodash _.keyBy() method creates an object composed of keys generated from the results of running each element of collection through iteratee. The corresponding value of each key is the last element that is responsible for generating the key.

Syntax:

_.keyBy( collection, iteratee )

Parameters:

• collection (Array|Object) parameter holds the collection to iterate over.
• iteratee(Function) parameter holds the iteratee to transform keys.

Return Value:

This method returns the composed aggregate object.

Example 1:

javascript

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array = [
    { 'dir': 'left', 'code': 89 },
    { 'dir': 'right', 'code': 71 }
];

// Use of _.keyBy() method
let keyby_array = _.keyBy(array, 'dir');

// Printing the output
console.log(keyby_array);

Output:

{ 'left': { 'dir': 'left', 'code': 89 }, 
'right': { 'dir': 'right', 'code': 71 } }

Example 2:

javascript

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array = [
    { 'dir': 'left', 'code': 89 },
    { 'dir': 'right', 'code': 71 }
];

// Use of _.keyBy() method
let keyby_array = _.keyBy(array, function (o) {
    return String.fromCharCode(o.code);
});

// Printing the output
console.log(keyby_array);

Output:

{ 'Y': { 'dir': 'left', 'code': 89 }, 
'G': { 'dir': 'right', 'code': 71 } }