ES5 extend object

extendObject.js

function extendObject(parent, child) {
    var copyFunction = function (f) {
            var t = function () {
                return f.apply(this, arguments);
            };
            Object.defineProperty(t, 'name', {
                value: f.name,
            });
            return t;
        },
        isObject = function (val) {
            return (typeof val === 'object' && val);
        },
        isFunction = function (val) {
            return (typeof val === 'function');
        },
        getType = function (val) {
            if (isObject(val)) return extendObject(val);
            if (isFunction(val)) return copyFunction(val);
            return val;
        };

    child = child || {};

    Object.keys(parent).forEach(function (p) {
        var list = [],
            val = parent[p];

        if (isObject(val)) {
            if (val instanceof Array) {
                for (var x = val.length; x--;) {
                    list[x] = getType(val[x]);
                }
                child[p] = list;
            }
            else {
                child[p] = extendObject(val);
            }
        }
        else if (isFunction(val)) {
            child[p] = copyFunction(val);
            Object.keys(val).forEach(function (fp) {
                child[p][fp] = getType(val[fp]);
            });
        }
        else {
            child[p] = val;
        }
    });

    return child;
}