JavaScript array cloning. Why is the browser hanging?

Question

JavaScript

function cloneArray(mas) {
  var masClone = new Array();
  for(i = 0; i < mas.length; i++) {
    masClone.push(mas[i]);
    for(j = 0; j < mas[i].length; j++) {
      masClone[i].push(mas[i][j]);
    }
  }
  return masClone;
}

var s1 = 0;
var s2 = 1;
var d1 = 1;
var d2 = 0;

var mass1 = [ 
s = [s1, s2],
d = [d1, d2]
];

var mass2 = cloneArray(mass1);

Here's the code. I just can’t understand why the browser hangs, it’s clear that it’s because of the cycle, but still it seems to be correct.

Answer 1

There's some kind of magic that I don't understand...

var mass1 = [ 
s = [s1, s2],
d = [d1, d2]
];

Here is the correct deep copy option (example and comparison with other jsfiddle.net/0yseqsuy solutions ):

var isArray = Array.isArray || function (arr) {
  return Object.prototype.toString.call(arr) === "[object Array]";
}

var isObject = function (obj) {
  return Object.prototype.toString.call(obj) === "[object Object]";
}

function cloneDeep(mas) {
  var masClone = isArray(mas) ? new Array(mas.length) : {};   
  
  Object.keys(mas).forEach(function (key) {
    if (isArray(mas[key]) || isObject(mas[key]))
      masClone[key] = cloneDeep(mas[key]);
    else
      masClone[key] = mas[key];
  });

  return masClone;
}

But older browsers need the Object.keys and forEach polyfills.