Cloning an Object

JavaScript performance comparison

Revision 68 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="http://code.jquery.com/jquery-1.5.1.js" type="text/javascript">
</script>
<script>
  var oldObject = {
    a: 1,
    b: 2,
    c: 3,
    d: new Date,
    e: 5,
    f: 9,
    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
    }
  });

  function structuredClone(obj) {
    var oldState = history.state;
    history.replaceState(obj);
    var clonedObj = history.state;
    history.replaceState(oldState);
    return clonedObj;
  }

  var pendingCallbacks = {};

  window.addEventListener('message', function(e) {
    var cloneId = e.data.cloneId,
        clonedValue = e.data.value;

    if (e.source === window && cloneId && cloneId in pendingCallbacks) {
      var callback = pendingCallbacks[cloneId];
      delete pendingCallbacks[cloneId];
      callback(clonedValue);
    }
  });

  var asyncStructuredClone = function(o, callback) {
      var cloneId = String(Math.random());
      pendingCallbacks[cloneId] = callback;
      window.postMessage({
        value: o,
        cloneId: cloneId
      }, '*');
      };
</script>
<script src="https://rawgithub.com/Jamtis/FluidWeb/master/FluidWeb/WebContent/lib/scripts/FluidWeb.js"
onload="FluidWeb.Module.provideSystemModule('Object')">
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
JQuery.extend deep
var newObject = jQuery.extend(true, {}, oldObject);
pending…
JSON
 
pending…
JQuery.extend
 
pending…
simple clone function
 
pending…
ES5 Object.clone
 
pending…
structured clone (using history)
var newObject = structuredClone(oldObject);
pending…
async structured clone (using postMessage)
// async test
asyncStructuredClone(oldObject, deferred.resolve);
pending…
FluidWeb Object clone
FluidWeb.Modules.Object.clone(oldObject);
pending…

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