Copy and clone object/array

    var objProto = Object.prototype,
        arrProto = Array.prototype,
        toString = objProto.toString,

    function isObj(obj) {

        if (toString.call(obj) === '[object Object]') {
            return true;
        }

        return false;
    }
    function isArray(obj) {

        if (toString.call(obj) === '[object Array]') {
            return true;
        }

        return false;
    }

    function copy(base, target, opt) {

        var key, i, l;

        opt || (opt = {});

        for (key in target) if (target.hasOwnProperty(key)) {

            if (base[key] && !opt.overwrite) {
                continue;
            }

            if (isObj(target[key]) && opt.deepCopy) {
                base[key] = copy({}, target[key]);
            }
            else if (isArray(target[key])) {
                if (opt.deepCopy) {
                    base[key] = [];

                    for (i = 0, l = target[key].length; i < l; i++) {
                        if (isObj(target[key][i])) {
                            base[key].push(copy({}, target[key][i]));
                        }
                        else {
                            base[key].push(target[key][i]);
                        }
                    }
                }
                else {
                    base[key] = target[key];
                }
            }
            else {
                base[key] = target[key];
            }
        }

        return base;
    }