Sota-class NPM

Sota-Class.js

This is package for javascript developers that cannot forget OOP.
In Node.js, we have util.inherits to do the inheritance stuffs, but it's not available in browser environment and also discouraged now.
New ES6 with language-level inheritance support is still not popular enough, and we have to use old syntax in many cases.
Then let's try Sota-Class. This module will bring you the familar OOP features with Java language. It's written in pure javscript, no dependency, works well on Node.js/browsers or any javascript environment.

Installation

Node.js

  npm install sota-class

Browser

The easiest way to use the library is with webpack or browserify

Usage

Make sub-class by `Class.extends(properties)`

Let's create the first class

var assert = require('assert');
var Class = require('sota-class').Class;
var Animal = Class.extends({
  classname: 'Animal',

  // The properties start with '$' are the static/class property
  $HABITAT: 'various',

  // The others will become the private properties of class instance
  age: 0,

  initialize: function(name) {
    this._name = name;
  },

  getName: function() {
    return this._name;
  },

  helloWorld: function() {
    throw new Error('Implement me in derived class');
  },

  destroy: function() {
    delete this._name;
  },

});

var foo = new Animal('Foo');
// Classname is defined in properties
assert.equal(Animal.classname, 'Animal');

// Class instance has the same classname value
assert.equal(foo.classname, 'Animal');

// Both class and class instance contain the static properties
assert.equal(Animal.HABITAT, 'various');
assert.equal(foo.HABITAT, 'various');

// Only the class instance has non-static properties
assert.equal(Animal.age, undefined);
assert.equal(foo.age, 0);

// Initialize method acts the constructor role
// and it's called automatically, then the name is set
assert.equal(foo.getName(), 'Foo');

And here's how to extends a existed class

var Cat = Animal.extends({
  classname: 'Cat',

  $HABITAT: 'kitchen',

  helloWorld: function() {
    return 'Meow';
  },
});

var cat = new Cat('Kitty');

// `initialize` and `getName` methods are inherited from Animal class
assert.equal(cat.getName(), 'Kitty');

// `helloWorld` is overrided
assert.equal(cat.helloWorld(), 'Meow');

// Defined property is overrided as well
assert.equal(Cat.HABITAT, 'kitchen');

How to call the super method

var Lion = Cat.extends({
  classname: 'Lion',

  // If the first parameter of a method is `$super`
  // It's the reference to the ancestor method
  getName: function($super) {
    return $super() + '-Lion';
  },
});

var lion = new Lion('Simba');
// Yeah, the name has the '-Lion' suffix
assert.equal(lion.getName(), 'Simba-Lion');

By default, the ancestor of methods initialize and destroy are called in their subclass' methods automatically, even if you don't do it explicitly

var Duck = Animal.extends({
  classname: 'Duck',

  initialize: function(name) {
    // Do nothing, don't call the ancestor explicitly
  },

  destroy: function() {
    // Also do nothing
  },
});

var duck = new Duck('Donald');
// The name is still set, because Animal's initialize was called automatically
assert.equal(duck.getName(), 'Donald');

// And after the destroy, the name is deleted
duck.destroy();
assert.equal(duck.getName(), undefined);

If you don't want initialize or destroy are called automatically, put the $super as the first method's argument and don't invoke it

var Weirdo = Animal.extends({
  initialize: function($super, name) {
    // I don't want a name
  },
});

var weirdo = new Weirdo('Awesome name');
// Since the initialize was not called, the weirdo's name was not set as well
assert.equal(weirdo.getName(), undefined);

Make the singleton by `Class.singleton(properties)`

The argument is similar with extends method. But the result is an object instead of Class

var Tom = Cat.singleton({
  // initialize method will be called automatically in hidden scope

  initialize: function($super) {
    // Of course, Tom is an unique creature
    // and doesn't need to pass his name from outside
    $super('Tom');
  },

  confess: function() {
    return 'ILoveJerry';
  },

});

assert.equal(Tom.getName(), 'Tom');
assert.equal(Tom.confess(), 'ILoveJerry');