cloning an object

JavaScript performance comparison

Revision 21 of this test case created by S

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="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.5.2/underscore-min.js"></script>
<script>
Benchmark.prototype.setup = function() {
    var oldObject = {
      a: 1,
      b: 2,
      c: 3,
      d: 4,
      e: 5,
      f: function() {
        return 6;
      },
      g: [7, 8, 9]
    };
   
   
    function clone(obj) {
      var target = {};
      for (var i in obj) {
        if (obj.hasOwnProperty(i)) {
          target[i] = obj[i];
        }
      }
      return target;
    }
   
    Object.defineProperties(Object, {
      'extend': {
        'configurable': true,
        'enumerable': false,
        'value': function extend(what, wit) {
          var extObj, witKeys = Object.keys(wit);
   
          extObj = Object.keys(what).length ? Object.clone(what) : {};
   
          witKeys.forEach(function(key) {
            Object.defineProperty(extObj, key, Object.getOwnPropertyDescriptor(wit, key));
          });
   
          return extObj;
        },
        'writable': true
      },
      'clone': {
        'configurable': true,
        'enumerable': false,
        'value': function clone(obj) {
          return Object.extend({}, obj);
        },
        'writable': true
      }
    });
};
</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 stringify/parse
var newObject = JSON.parse(JSON.stringify(oldObject));
pending…
jQuery.extend()
var newObject = jQuery.extend({}, oldObject);
pending…
clone function
var newObject = clone(oldObject);
pending…
ES5 Object.clone
var newObject = Object.clone(oldObject);
pending…
Underscore _.clone
var newObject = _.clone(oldObject);
pending…
Object.create
var newObject = Object.create(oldObject);
pending…

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