Cloning an Object (v23)

Revision 23 of this benchmark created by Jesper Petersson on

Description

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. (see Revision 3 by Corban Brook)

Revision 22: added LoDash since someone brought Underscore, using CDN for UnderScore

Preparation HTML

<script src="http://code.jquery.com/jquery-1.5.1.js" type="text/javascript"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.3.3/underscore-min.js"></script>
<script>var underscore = _.noConflict();</script>
<script src="https://raw.github.com/bestiejs/lodash/master/lodash.min.js"></script>
<script>var lodash = _.noConflict();</script>
<script>
  //allow UnderScore vs LoDash
  var lodash = window.lodash,
      underscore = window.underscore;

  //continue test setup
  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;
  }

  function clone_deep(obj) {
    var target = {};
    for (var i in obj) {
      if (typeof(obj) === 'object') {
        target[i] = clone_deep(obj[i]);
      }
      else {
        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>

Test runner

Ready to run.

Testing in
TestOps/sec
JQuery.extend deep
var newObject = jQuery.extend(true, {}, oldObject);
ready
JSON
var newObject = JSON.parse(JSON.stringify(oldObject));
ready
JQuery.extend
var newObject = jQuery.extend({}, oldObject);
ready
simple clone function
var newObject = clone(oldObject);
ready
ES5 Object.clone
var newObject = Object.clone(oldObject);
ready
slice(0)
var newObject = oldObject.slice(0);
ready
underscore.clone
var newObject = underscore.clone(oldObject);
ready
lodash.clone
var newObject = lodash.clone(oldObject);
ready
clone_deep
var newObject = clone_deep(oldObject);
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.