node-extnd

Extnd

Extend is based off Jon Resig's Simple JavaScript Inhertitance blog post with the added support for multiple inheritance and AMD & CommonJS loaders. It is also lint-free and removes a superfluous check which breaks Closure Compiler. This inheritence system has been tested on large production apps for desktop and mobile.

It is recommended you import extnd.js using a CommonJS or AMD loader. Otherwise Class will be added to window and you could have name collisions.

Usage

For your constructor method use init instead.

var Animal = Class.extnd({
    init: function (name) {
        this.name = name;
    },
 
    getName: function () {
        return this.name;
    }
});

And to inherit:

var Bird = Animal.extnd({
    init: function () {
        this._super.apply(this, arguments);
        console.log('Animal says my name is', this.getName());
    }
});

Note in the example above we call the parent method with this._super. This reference is dynamic in a way that supports multiple inheritance. You can of course call it in any way you would call a normal method:

this._super([arg1[, arg2[, ...]]);
this._super.call(thisArg[, arg1[, arg2[, ...]]);
this._super.apply(thisArg, [argsArray]);

You can string extensions together (multiple inheritance):

var HummingBird = Animal.extnd(Bird).extnd({
    flapsVeryFast: true,
    carefulWithThisObject: {
        flapCount: 0
    },
 
    fastFlapping: function () {
        // wow, much flapping
        this.carefulWithThisObject.flapCount++;
    }
});

It is worth noting that flapsVeryFast and carefulWithThisObject variable exists in the class-scope. flapsVeryFast is a primitive and so it will be copied to all instances. However carefulWithThisObject is an Object and it will be shared, therefore making a flapCount incrementor here a bad idea as all instances will increment it. To create variables in instance-scope create them inside a Function e.g. this.carefulWithThisObject = ...

License

Released under the MIT license (see LICENSE for jargon).

Credits

Michal Kot for his multiple inheritance idea