Question

I found this wonderful clone function for javascript (http://my.opera.com/GreyWyvern/blog/show.dml/1725165), but it breaks with jquery with the error:

Uncaught TypeError: Object function [removed] has no method ‘replace’

Here’s the function:

Object.prototype.clone = function() {
    var newObj = (this instanceof Array) ? [] : {};
    for (i in this) 
    {
        if (i == 'clone') continue;

        if (this[i] && typeof this[i] == "object")
            newObj[i] = this[i].clone();
        else 
            newObj[i] = this[i]
    } 
    return newObj;
};

What does replace have to do with anything?

Answer 1

When you extend Object.prototype, you’re taking a risk. It forces all for-in enumeration to add hasOwnProperty to ensure the Object.prototype extension isn’t included.

jQuery doesn’t always include that check, presumably because of the performance impact. So somewhere along the line it’s coming across your clone function in the wrong place.

You’ll be better off not having it on Object.prototype, but rather having it directly on Object.

Object.clone = function(obj) {
    var newObj = (this instanceof Array) ? [] : {};
    for (i in this)  {

        if (obj[i] && typeof obj[i] == "object")
            newObj[i] = Object.clone(obj[i]);
        else 
            newObj[i] = obj[i]
    } 
    return newObj;
};

Then call it from the object…

var clone = Object.clone(some_object);

---

Notice that the original function had the line…

if (i == 'clone') continue;

This means that you could never clone a property named clone. This is obviously not a good thing.