Cloning an Object

JavaScript performance comparison

Revision 57 of this test case created

Info

There is no quick and easy facility for cloning an object, Some people recommend using JQuery.extend others JSON.parse/stringify

http://stackoverflow.com/questions/122102/what-is-the-most-efficient-way-to-clone-a-javascript-object

If you want the fastest possible clone function. I would personally anticipate the data structure of your object and write a custom clone to handle it.

Preparation code

<script src="http://code.jquery.com/jquery-1.5.1.js" type="text/javascript">
</script>
<script>
  var oldObject = {
    a: 1,
    b: 2,
    c: 3,
    d: 4,
    e: 5,
    g: {
      a: [7, 8, 9, 54.6435, 354, 353, 453.4, 534, 53.4, 5.34, 52.4, 234, 6, 678, 76.84, 53, 73, 54.2, 57, 45, 3, 67, 78, 7265, 7, 546, 37, 8, 6, 8, 436.4, 64.3, 6, 8, 7, 6, 74.7, 3634.636, 43.6, 567.8735, 3675, 7346, 834, 737643, 6, 7436, 57, 47, 57.46, 57, 46, 74.6, 7, 56.7, 26.3, 67.7, 5474.5745, 754, 754, 745, 7],
      b: [354, 35, 1, 312, 32.4, 35, 7, 76878.8, 686.7, 78.98, 77, 46.3, 3452, 13, 435, 4, 86.7, 987.89, 86775.6, 4565, 88.9, 9, 6, 75678, 9, 9067, 46, 356.65, 8.95, 246.5, 87, 678, 465.6, 86.8, 63, 56, 867.86, 43, 65.67, 586.85, 734, 77, 867, 43, 6, 67, 67.864757, 86, 8, 3.62, 5, 6, 767, 9878.85, 4.6, 867, 7436, 7, 4, 721, 5, 765, 8, 6, 3245, 7548, 53.67, 437.6],
      c: [7, 8, 9, 54.6435, 354, 353, 453.4, 534, 53.4, 5.34, 52.4, 234, 6, 678, 76.84, 53, 73, 54.2, 57, 45, 3, 67, 78, 726.5, 7, 54.6, 37, 8, 6, 8, 436.4, 64.3, 6, 8, 7, 6, 74.7, 3634.636, 43.6, 567.86735, 3675, 734.6, 834, 737.643, 6, 74.36, 57, 47, 57.46, 57, 46, 74.6, 7, 56.7, 26.3, 67.7, 5474.5745, 754, 754, 74.5, 7]
    }
  };


  var object_create = Object.create;
  if (typeof object_create !== 'function') {
    object_create = function(o) {
      function F() {}
      F.prototype = o;
      return new F();
    };
  }

  function deepCopy(src) {
    if (src === null || typeof(src) !== 'object') {
      return src;
    }

    //Honor native/custom clone methods
    if (typeof src.clone === 'function') {
      return src.clone(true);
    }

    //Special cases:
    //Date
    if (src instanceof Date) {
      return new Date(src.getTime());
    }
    //RegExp
    if (src instanceof RegExp) {
      return new RegExp(src);
    }
    //DOM Elements
    if (src.nodeType && typeof src.cloneNode === 'function') {
      return src.cloneNode(deep);
    }

    var proto = (Object.getPrototypeOf ? Object.getPrototypeOf(src) : src.__proto__);
    if (!proto) {
      proto = src.constructor.prototype;
    }
    var ret = object_create(proto);

    for (var key in src) {
      ret[key] = deepCopy(src[key]);
    }
    return ret;
  }
</script>

Preparation code output

Test runner

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Testing in unknown unknown
Test Ops/sec
JQuery.extend deep
var newObject = jQuery.extend(true, {}, oldObject);
pending…
JSON
var newObject = JSON.parse(JSON.stringify(oldObject));
pending…
JQuery.extend
var newObject = jQuery.extend({}, oldObject);
pending…
simple deep clone function
var newObject = deepCopy(oldObject);
pending…

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