object-proto-aliases.js

/**
 * Aliases and additional "sugar"
 * 2010-04-15
 * @author Dmitry A. Soshnikov
 */
(function () {

    ["defineProperty", "defineProperties", "keys", "getOwnPropertyNames",
    "getOwnPropertyDescriptor", "getPrototypeOf", "seal", "freeze",
    "preventExtensions", "isFrozen", "isSealed", "isExtensible"]

        .forEach(function (methodName) {

            var newMethodName = (
                methodName == "getPrototypeOf"
                    ? "getPrototype"
                    : methodName
            );

            Object.defineProperty(Object.prototype, newMethodName, {

                // use function (as in spec), but for some properties -
                // getter is better, e.g. o.keys - for what to make it as a method?
                value: function () {
                    return Object[methodName].apply(
                        Object,
                        [this].concat([].slice.call(arguments))
                    );
                }

            });
        });

    /**
     * forAll
     * iterates over all properties of an object
     * including those with [[Enumerable]] false,
     * analysing prototype chain as well
     */
    Object.defineProperty(Object.prototype, "forAll", {

        value: function (fn) {

            var
                self = this,
                object = self;

            do {

                object.getOwnPropertyNames().forEach(function (name) {
                    if (!fn.call(
                        self, // reciever
                        name, // property name
                        object[name], // value
                        object, // real owner
                        object.getOwnPropertyDescriptor(name).enumerable // is it enumerable
                     ))
                        return false;
                });

            } while (object = object.getPrototype());

        }
    });

})();

var o = {x: 10, y: 20};

o.defineProperty("z", {
    value: 100,
    enumerable: false
});

print(o.keys()); // x,y, but not z
print(o.z); // 100

print(o.getOwnPropertyNames()); // x,y,z

print(o.getOwnPropertyDescriptor("z").enumerable); // false

print(o.seal());
print(o.isSealed()); // true

// show all properties of an object
// including inherited and with {enumerable: false}
o.forAll(function (name, value, realOwner, enumerable) {

    print('Property "' + name +'" with value ' + value + "\n");

    // test for real owner
    realOwner != this && print("\t- " + name + " property is inherited\n");

    // and show [[Enumerable]] false properties
    !enumerable && print("\t- " + name + " isn't enumerable\n");

});

var object = Object.create(o)
    .preventExtensions();

print(object.isExtensible()); // false

print(object.getPrototype() === o); // true
print(o.isPrototypeOf(object)); // true