Question

91

JavaScript: clone a function

rated 0 times [ 92] [ 1] / answers: 1 / hits: 133651 / 15 Years ago, wed, december 2, 2009, 12:00:00

What is a fastest way to clone a function in JavaScript (with or without its properties)?

Two options coming to mind are eval(func.toString()) and function() { return func.apply(..) }. But I am worried about performance of eval and wrapping will make stack worse and will probably degrade performance if applied a lot or applied to already wrapped.

new Function(args, body) looks nice, but how exactly can I reliable split existing function to args and body without a JS parser in JS?

Update:
What I mean is being able to do

var funcB = funcA.clone(); // where clone() is my extension

funcB.newField = {...};    // without affecting funcA

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zoiel

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answered 15 Years ago lucianom · Accepted Answer

try this:

var x = function() {

    return 1;

};



var t = function(a,b,c) {

    return a+b+c;

};





Function.prototype.clone = function() {

    var that = this;

    var temp = function temporary() { return that.apply(this, arguments); };

    for(var key in this) {

        if (this.hasOwnProperty(key)) {

            temp[key] = this[key];

        }

    }

    return temp;

};



alert(x === x.clone());

alert(x() === x.clone()());



alert(t === t.clone());

alert(t(1,1,1) === t.clone()(1,1,1));

alert(t.clone()(1,1,1));