cloning an object

JavaScript performance comparison

Revision 55 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="//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 cloneDeep = function(obj) {
      // Handle string, int, boolean, null or undefined
      if (null == obj || "object" != typeof obj) {
        return obj;
      }
   
      var copy;
      // Handle Date
      if (obj instanceof Date) {
        copy = new Date();
        copy.setTime(obj.getTime());
        return copy;
      }
   
      // Handle Array
      if (obj instanceof Array) {
        copy = [];
        for (var i = 0, len = obj.length; i < len; i++) {
          copy[i] = cloneDeep(obj[i]);
        }
        return copy;
      }
   
      // Handle Object
      if (obj instanceof Object) {
        copy = {};
        for (var attr in obj) {
          if (obj.hasOwnProperty(attr)) {
            copy[attr] = cloneDeep(obj[attr]);
          }
        }
        return copy;
      }
   
      console.error("Unable to copy object! Its type isn't supported.", obj);
    }
   
      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…
sharc cloneDeep
var newObject = cloneDeep(oldObject);
pending…

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