Extend JS

extend.js

function extend(object) {
    if (arguments.length > 1) {
        for (var i = 1; i < arguments.length; ++i) {
            for (j in arguments[i]) {
                object[j] = arguments[i][j];
            }
        }
    }
    return object;
}

usage.js

function MyClass() {
}

extend(MyClass.prototype, {
  method: function() { return 10 }
});

o = new MyClass();
console.log(o.method()); // Outputs 10

extend(o, {
  other: function() { return 20 },
  method: function() { return 30 }
});

console.log(o.method()); // Outputs 30
console.log(o.other()); // Outputs 20