create new arrays for repeating elements in javascript

Question

I have a JavaScript array with 8 elements and some elements are repeating. I want to create separate arrays for identical elements.

example: original a

Answer 1

var arr = [1,1,1,3,3,1,2,2];

var hash = Object.create(null);

var result = arr.reduce(function(r, n) {
  if(!hash[n]) {
    hash[n] = [];
    r.push(hash[n]);
  }
  
  hash[n].push(n);
  
  return r;
}, []);

console.log(result);

And an ES6 solution that uses Map, and spread:

const arr = [1,1,1,3,3,1,2,2];

const result = [...arr.reduce((r, n) =>
  r.set(n, (r.get(n) || []).concat(n)),
new Map()).values()];

console.log(result);