js-class

Define classes in Javascript

npm install js-class
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Define Classes in Javascript

This is a simple module providing a simple Class function to simplify class definition in Javascript.

Install

For Node.js

npm install js-class

For browser, use bower

bower install js-class

To rebuild js-class.min.js, type:

npm install
npm run-script build

How to Use

With Node.js:

var Class = require('js-class');

In browser, just include js-class.min.js

Prototype

Class(baseClass, prototype, options);

Parameters

  • baseClass: baseClass type, optional, default is Object;
  • prototype: the prototype for new class;
  • options: other options like implements and statics, see details below.

Returns

The newly defined class.

Details

A simple and quick sample:

var Class = require('js-class');

var MyClass = Class({
  constructor: function (value) {
    // this is the constructor
    this._value = value;
  },

  print: function () {
    console.log(this._value);
  },

  // getter/setter is supported
  get value () {
    return this._value;
  },

  set value (value) {
    if (!isFinite(value)) {
      throw new Error('Bad Value');
    }
    this._value = value;
  }
});

var myObject = new MyClass(1);
myObject.print(); // get 1
myObject.value = myObject.value + 100;
myObject.print(); // get 101

A simple inheritance sample:

var BaseClass = Class({
  constructor: function (value) {
    this.value = value;
  },

  print: function () {
    console.log('BaseClass: %d', this.value);
  }
});

var SubClass = Class(BaseClass, {
  constructor: function (val1, val2) {
    BaseClass.prototype.constructor.call(this, val1 + val2);
  },

  print: function () {
    console.log('SubClass');
    BaseClass.prototype.print.call(this);
  }
});

var myObject = new SubClass(1, 2);
myObject instanceof SubClass;   // true
myObject instanceof BaseClass;  // true
myObject.print();
// get
// SubClass
// BaseClass: 3

Multiple inheritance with implements

var ActiveBuffer = Class(Buffer, {
  // override Clearable
  clear: function () {
    // TODO I hate to be cleared
    this.emit('cleared');
  }
}, {
  implements: [EventEmitter, Clearable]
});

var buffer = new ActiveBuffer().on('cleared', function () { console.log('CLEARED'); });
buffer.clear();

buffer instanceof Buffer; // true
buffer instanceof EventEmitter; // false
buffer instanceof Clearable;  // false

Static members

var Singleton = Class({
  constructor: function () {
    // ...
  },

  work: function () {
    // ...
  }
}, {
  statics: {
    get instance () {
      if (!Singleton._instance) {
        Singleton._instance = new Singleton();
      }
      return Singleton._instance;
    }
  }
});

Singleton.instance.work();

Type Information

The keyword instanceof can be used to check the type inherited directly. But it doesn't work with implemented types. Use Class.is for all the cases:

Class.is(object).typeOf(Type)

We also have two aliases:

Class.is(object).a(Type)
Class.is(object).an(Object)

License

MIT/X11 License

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