SubClass.js

subclass.js

subClass = function (source, prototype) {

    var dummy = new source.constructor;

    for (var key in prototype) {
        dummy[key] = prototype[key];
    }

    source.__proto__ = dummy;
}

// Array
source = [1,2,3];
prototype = {
    alert : function () {
        alert(this);
    }
}

subClass(source, prototype);

source.alert(); // 1, 2, 3
[1, 2, 3].alert(); // undefined

// Date
source = new Date();
prototype = {
    alert : function () {
        alert(this);
    }
}

subClass(source, prototype);

source.alert(); // Date
new Date().alert(); // undefined