A nice and simple clone function.

clone.js

var clone = function clone(src) {
    var r, i, l,
        mixin = function(dest, source, copyFunc) {
            var name, s, i, empty = {};
            for(name in source){
                s = source[name];
                if(!(name in dest) || (dest[name] !== s && (!(name in empty) || empty[name] !== s))){
                    dest[name] = copyFunc ? copyFunc(s) : s;
                }
            }
            return dest;
        };

    if(!src || typeof src != "object" || Object.prototype.toString.call(src) === "[object Function]")
        return src;

    if(src.nodeType && "cloneNode" in src)
        return src.cloneNode(true);

    if(src instanceof Date)
        return new Date(src.getTime());

    if(src instanceof RegExp)
        return new RegExp(src);

    if(src && (src instanceof Array || typeof src == "array")){
        r = [];
        for(i = 0, l = src.length; i < l; ++i){
            if(i in src)
                r.push(clone(src[i]));
        }
    }
    else
        r = src.constructor ? new src.constructor() : {};

    return mixin(r, src, clone);
};