Check if some elements of array are equal JavaScript

We have an array of numbers that have got some redundant entries, our job is to write a function that takes in the array and groups all the identical entries into one subarray and returns the new array thus formed.

For example −

//If the input array is:
const arr = [1, 3, 3, 1];
//then the output should be:
const output = [[1, 1], [3, 3]];

We will use a HashMap to keep a track of the elements already occurred and iterate over the array using a for loop, the code for this will be −

Example

const arr = [1, 3, 3, 1];
const groupArray = arr => {
   const map = {};
   const group = [];
   for(let i = 0; i 
Output
The output in the console will be −
[ [ 1, 1 ], [ 3, 3 ] ]