Nodejs Utililty Methods Array Equal Check

Array.prototype.isEqual = function(a){
  if(this.length!=a.length) return false;
  for(var i=0;i<this.length;i++){
    if(this[i] instanceof Array){
      if(!(a[i] instanceof Array)) return false;
      if(!this[i].isEqual(a[i])) return false;
    }else{
      if(this[i]!=a[i]) return false;
  return true;

const a = [1, 2, 3];
const b = [1, 2, 3];
Array.prototype.isEqual = function (arr) {
  function check(arr1, arr2) {
    for (let i = 0, len = arr1.length; i < len; i++) {
      const bool = arr2.some(function (item) {
        return Object.is(arr1[i], item);
      });
      if (!bool) return false;
...

"use strict";
Array.prototype.isEqual = function(target){
  if (this == target) return true;
  if (this == null || target == null) return false;
  if (this.length != target.length) return false;
  for(var i in this){
    if (
      (this[i] !== target[i]) &&
      (typeof this[i].isEqual != "function" ||
...