Class4js NPM | npm.io

class4js

The class4js library is for class-driven development in JavaScript. It allows to emulate classes in JavaScript. Library based on ECMAScript 5 API and implements open/close principle. When class is created, class is closed for modifications.

The Open/Close principle

A module should be open for extension but closed for modifications.

Installation

npm install class4js

API

Private class members are decorated with _ and protected with .

Create class

Creates a class:

class4js.Class.create(properties:Object, parent:Object): Object

$class(properties:Object, parent:Object): Object

Example

"use strict";

require("class4js");

var Person = $class({
  __construct__: function (name) {
    this.__name = name;
  },
  getName: function () {
    return this.__name;
  }
});

var person = new Person("John Smith");

console.log(person.getName());

Fields

All class fields should be defined as class members or initialized in constructor, because when class is created, class is closed for modifications.

Example

"use strict";

require("class4js");

var Person = $class({
    __age: 30,
    __construct__: function (name) {
    this.__name = name;
  },
  getName: function () {
    return this.__name;
  },
  getAge: function () {
    return this.__age;
  },
  setGender: function (gender) {
    // It's to late to initialize a class field:
    this.__gender = gender;
  }
});

var person = new Person("John Smith");

console.log(person.getName());
console.log(person.getAge());

// Error will be raised here:
person.setGender("male");

Constants

Use NAMES_LIKE_THIS for constants.

Example

"use strict";

require("class4js");

var Person = $class({
  MAX_AGE: 99,
  __construct__: function () {
  }
});

console.log(Person.MAX_AGE);

Properties

A property is a member that provides a flexible mechanism to read, write, or compute the value of a private field:

Example

"use strict";

require("class4js");

var Person = $class({
  __construct__: function (name) {
    this.__name = name;
    this.__created = new Date();
  },
  name: {
    get: function () {
      return this.__name;
    },
    set: function (value) {
      this.__name = value;
    }
  },
  created: {
    get: function () {
      return this.__created;
    }
  }
});

var person = new Person();
person.name = "John Smith";

console.log(person.name);
console.log(person.created);

Static members

class4js library allows to define static class members:

Example

"use strict";

require("class4js");

var Calculator = $class({
  __static__: {
    sum: function (a, b) {
      return a + b;
    },
    subtract: function (a, b) {
      return a - b;
    }
  }
}); 

console.log(Calculator.sum(2, 2));
console.log(Calculator.subtract(8, 4));

Inheritance

Creates a class with the specified parent:

Example

"use strict";

require("class4js");

var Shape = $class({
  __construct__: function () {
  },
  draw: function () {
    console.log("Shape is drawn...");
  }
});

var Rectangle = $class({
  __construct__: function () {
  },
  draw: function () {
    this._super.draw();
    console.log("Rectangle is drawn...");
  }
}, Shape); 

var rec = new Rectangle();
rec.draw();