Nodejs Utililty Methods Array Different

function diffArray(arr1, arr2) {
  let newArr1 = [];
  let newArr2 = [];
  let sliced = [];
  for (let y = 0; y < arr1.length; y++) {
    if (arr2.includes(arr1[y]) === false) {
      newArr1.push(y);
  for (let i = 0; i < newArr1.length; i++) {
    sliced.push(arr1.splice(newArr1[0], 1));
  for (let x = 0; x < arr2.length; x++) {
    if (arr1.includes(arr2[x]) === false) {
      newArr2.push(x);
  for (let j = 0; j < newArr2.length; j++) {
    sliced.push(arr2.splice(newArr2[0], 1));
  let finalArr = [].concat.apply([], sliced);
    return finalArr;
diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]);

Array.prototype.difference = function(t)
    var t = t.toHash();
    var r = [];
    this.forEach(function (item) { if (!t.containsKey(item)) r.push(item); });
    return r;