example.js

var numbers = [1, 5, 17, 4, 9, 3, 1, 17, 32, 5, 3, 27, 9, 18, 3, 12, 67, 18, 32, 1, 19, 21, 1, 17];
var hashMap = {};
var groupArr = [];
var currentNum;

for (var i = 0; i < numbers.length; i++) {
  currentNum = numbers[i];
  if (typeof hashMap[currentNum] === 'undefined') {
    hashMap[currentNum] = 0;
  }
  hashMap[currentNum] += 1;
}

for (var prop in hashMap) {
	if (!hashMap.hasOwnProperty(prop)) {
    break;
  }
  groupArr.push(prop + ':' + hashMap[prop]);
}

document.getElementById("arrayGrouped2").innerHTML = groupArr.join(',');

// => 1:4,3:3,4:1,5:2,9:2,12:1,17:3,18:2,19:1,21:1,27:1,32:2,67:1