cloning an object

JavaScript performance comparison

Revision 4 of this test case created by Jeff Monschke

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>
Benchmark.prototype.setup = function() {
    var oldObject = {
       a: 1,
       b: 2,
       c: 3,
       d: 4,
       e: 5,
       f: function() {
        return 6;
       },
       g: [7, 8, 9]
      };
   
    var oldArray = [1, 2, 3, 4, 5, function() {
        return 6;
       }, [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…
stringify eval
var newObject = eval("("+JSON.stringify(oldObject)+")");
pending…
jQuery.extend() Array
var newArray = jQuery.extend([], oldArray);
pending…

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