Lodash _.groupBy() Method

Lodash's _.groupBy() method groups elements of a collection into an object, using the results of an iterated function as keys, with corresponding arrays of elements that generate each key.

Syntax:

_.groupBy(collection, [iteratee]);

Parameters:

• Collection: It is the collection that the method iterates over.
• Iteratee: It is the function that is invoked for every element in the array.

Return Value: This method returns the composed aggregate object.

Example 1: In this example, we are composing an array-by-length function where the array is grouped by the length of the strings.

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

// Original array 
let users = (['eight', 'nine', 'four', 'seven']);

// Using of _.groupBy() method
// with the `_.property` iteratee shorthand 
let grouped_data = _.groupBy(users, 'length')

console.log(grouped_data);

Output:

{ '4': [ 'nine', 'four' ], '5': [ 'eight', 'seven' ]}

Example 2: In this example, we are composing an array by in which array is grouped according to the Math.floor function.

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

// Original array 
let users = (['one', 'two', 'three', 'four']);
let obj = ([3.1, 1.2, 3.3]);

// Using the _.groupBy() method
// with the `_.property` iteratee shorthand 
let grouped_data = _.groupBy(users, 'length')
let grouped_data2 = _.groupBy(obj, Math.floor)

// Printing the output 
console.log(grouped_data, grouped_data2);

Output:

{ '3': [ 'one', 'two' ], '4': [ 'four' ], '5': [ 'three' ] } 
{ '1': [ 1.2 ], '3': [ 3.1, 3.3 ] }