Cloning an Object

JavaScript performance comparison

Revision 84 of this test case created by Yannick Albert

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-2.0.3.js" type="text/javascript"></script>


<script>
  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
   }
  });

//Crockford clone function
function object(o) {
    function F() {}
    F.prototype = o;
    return new F();
}

// Nodejs util _extend
function nodeextend (origin, add) {
  // Don't do anything if add isn't an object
  if (!add || typeof add !== 'object') return origin;

  var keys = Object.keys(add);
  var i = keys.length;
  while (i--) {
    origin[keys[i]] = add[keys[i]];
  }
  return origin;
};


function recursive(obj){
    if(obj == null || typeof(obj) != 'object')
        return obj;

    var temp = obj.constructor(); // changed

    for(var key in obj)
        temp[key] = recursive(obj[key]);
    return temp;
}
</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 clone function
var newObject = clone(oldObject);
pending…
ES5 Object.clone
var newObject = Object.clone(oldObject);
pending…
Crockford Clone Function
var newObject = object(oldObject);
pending…
    var newObject = {};
    for (var k in oldObject){
    newObject[k]=oldObject[k];  
    }
 
pending…
Nodejs require('util')._extend
var newObject = nodeextend({}, oldObject);
pending…
recursive
var newObject = recursive(oldObject);
pending…

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