Easy prototype and static methods inheritance via inheritedBy method

npm install objex
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objex Build Status

Base constructor to ease prototype inheritance.

Skip to API.

Simple example

var Objex = require('objex'),

    Animal = Objex.create(function() {
        Animal.__super.apply(this, arguments);
        this.feet = 4;
        this.hands = 0;
        this.head = 1;

    Wolf = Animal.create(),

    Dog = Wolf.create(),

    Monkey = Animal.create(function() {
        Monkey.__super.apply(this, arguments);

        this.feet = 2;
        this.hands = 2;

    wolf = new Wolf(),
    dog = new Dog(),
    monkey = new Monkey();

// check inheritance
console.log('wolf is instance of Wolf', wolf instanceof Wolf);
console.log('wolf is instance of Animal', wolf instanceof Animal);

console.log('monkey is instance of Monkey', monkey instanceof Monkey);
console.log('monkey is instance of Animal', monkey instanceof Animal);

console.log('dog is instance of Dog', dog instanceof Dog);
console.log('dog is instance of Wolf', dog instanceof Wolf);
console.log('dog is instance of Animal', dog instanceof Animal);

Don't copy / partially copy static properties of super-class

var Animal = Objex.create(function() {
        Animal.__super.apply(this, arguments);

Animal.count = 0;

Animal.kill = function() {
    if (Animal.count > 0) {

// pass `false` as first argument to prevent static fields bypass,
// static method `create` will be copied anyway.
// Assume, you want to count sheeps separately.
// Animal.count will not be copied to Sheep.count, because it useless here.
// Animal.kill will not be copied to Sheep too, aren't you want to shoot your own Sheep?
Sheep = Animal.create(false, function() {

Sheep.count = 0;

// pass array of property names as first argument 
// to copy certain static properties only.
// Static property `count` is useless for Wolf,
// but you are still able to kill it, and decrease global Animal.count!
Wolf = Animal.create(['kill'], function() {
    Wolf.__super.apply(this, arguments);
    this.hungry = false;

Set base constructor which differs from the Object

Suppose, you need to create Error inheritor, so your prototype chain must look like ErrorEx > Error > Object, not ErrorEx > Object.

Objex.wrap at your service!

var MyOwnErrorEx;

function ErrorEx() {
    ErrorEx.__super.apply(this, arguments);

    this.extended = true;

util.inherits(ErrorEx, Error);
Objex.wrap(ErrorEx, Error);
// now ErrorEx has `create` method and `__super` property

MyOwnErrorEx = ErrorEx.create(function(code) {
    this.code = code;
    MyOwnErrorEx.__super.apply(this, Array.prototype.slice.call(arguments, 1));


Mixin (copy) static and prototype properties from any constructor to the Objex successor, without prototype chain modification. Mixed properties will be own properties of a target object.

var Animal = Objex.create(),
    Dog = Animal.create(),
    TrickyPet = function() {}, // mixin ctor
    LoudVoice = function() {}, // more one
    jimmy = new Dog();

Animal.prototype.say = function(wat) {

// mixin method
TrickyPet.prototype.jumpBackward = function() {

// copy TrickyPet.prototype methods to Dog.prototype

// call copied method from the instance of Dog

// mixin method
LoudVoice.prototype.say = function(wat) {
    console.log('(loud voice)', wat);

// override existing Dog prototype's method `say`
Dog.mixin({ override : true }, LoudVoice);


Dynamic mixing

You can declare special static method __objexOnMixing in the mixin, which will be called while mixin applies:

var Human = Objex.create(function() {
        Human.__super.apply(this, arguments);
    Mutant = function() {}; // mixin

Human.population = 1000;

Human.prototype.doSomething = function() {
    console.log('Doing something...');

Mutant.__objexOnMixing = function(Base, isHungry) {
    var doSomething = Base.prototype.doSomething;

    if (isHungry && typeof doSomething === 'function') {
        // extend Base method if Mutant is hungry
        Base.prototype.doSomething = function() {
            // eat anybody before doing something
            return doSomething.apply(this, arguments);

// people became hungry mutants
Human.mixin(Mutant, true);

var human = new Human();

console.log(Human.population); // -> 1001

human.doSomething(); // -> 'Doing something...'

console.log(Human.population); // -> 1000


Description of the Objex and its successors static methods.

create([options], ctor)

Create successor of the callee with constructor passed as ctor argument. Argument options describes how the successor inherits statis fields:

  • true – default value; copy all static properties w/o existing properties overriding;
  • false – don't copy statis properties;
  • { include : [], exclude : [] } – object with optional fields include and exclude which are arrays of properties' names to copy of not;
  • Array of String – shotcut syntax for { include : [] }.


Add Objex create and mixin static methods to the ctor which is not Objex successor without prototype chain modification.

mixin([options], ctor)

Mixin (copy) static and prototype methods of ctor to the callee contructor and its prototype if they doesn't exists.

Argument options is mostly the same as of the create method, but the object argument can contain additional boolean property override. If it equals true existing methods of the callee will be overriden by mixin's methods.

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