I haven’t posted for a while as I’ve been busy but I thought I’d post about object cloning because it’s a useful tip and can be used in many situations like browser hacking or general web development. I posted this to the sla.ckers forum a while ago but in case you missed it here goes….
When cloning a object in Javascript many of the examples I found used for(i in..) to traverse the properties and copy each of them. There is a nicer way to do this using the uneval function like this:-
obj={a:1,a:2} function clone(o) { return eval(uneval(o)); } obj2 = clone(obj); obj2.a=0; alert(obj.a); alert(obj2.a);
Giorgio Maone pointed out that it would be nice to prototype the code to make it easier to implement:-
Object.prototype.clone = function() { return eval(uneval(this)); } alert("test".clone()); alert((3).clone()); alert(clone.clone());
Comments 7
Hi Gareth,
Great tips! Unfortunately, if the object contains a reference to an HTML or XML element, those references is not cloned (of course). Which in turn makes this solution a little inadequate.
Yet, thanx for the trick!
Posted 10 Apr 2008 at 9:54 am ¶of course that works with FF and a few other browsers only. The more universal way of doing the same is exactly what I used in CoreAPI: http://www.gnucitizen.org/projects/coreapi/
CoreAPI.clone = function (o) {
function c(o) {
for (var i in o) {
this[i] = o[i];
}
}
return new c(o);
Posted 10 Apr 2008 at 11:05 am ¶};
@pdp
Damn I thought it worked in IE7 ah well neat trick anyways
Posted 10 Apr 2008 at 12:43 pm ¶It is bad practice to mingle with Object.prototype because it messes up property enumeration. Just google “Object.prototype is verboten” and a zillion arguments will appear. The Prototype JavaScript library once did this in 1.3 - with bad results.
Posted 10 Apr 2008 at 5:08 pm ¶The fix is to instead tack methods on to the global Object. For example:
Object.clone = function(object) { return eval(uneval(object)); };
@kourge
Nice tip and good point
Posted 10 Apr 2008 at 5:19 pm ¶Have you not about c & c++ ’s book ?
Posted 20 Apr 2008 at 6:38 pm ¶Post my E-mail,thank you
Your eval/uneval idea inspired me a cross-browser solution for those using YUI:
function clone = function( obj ) {
return YAHOO.lang.JSON.parse( YAHOO.lang.JSON.stringify( obj ) );
}
Tested fine with IE6 and FF2. Especially convenient for cloning arrays, hashs of arrays, arrays of hashs, etc.
Not sure about the performances. Might slow down your app if used to massively clone objects…
Posted 09 May 2008 at 5:29 pm ¶Post a Comment