Initialize.js

A JavaScript library for convenient object initialization

Many JavaScript programmers prefer using Object.create() over new and the constructor pattern. However, some may find the fact that the constructor pattern automatically calls a constructor function to be an advantage over Object.create(). Oftentimes, users of Object.create() must remember to call an init function to put the newly created object into a valid state. Initialize.js offers another object initialization option by combining the behavior of Object.create() while automatically calling the object's init() function, if present.

Without Initialize.js, a user of Object.create() must remember to call an initialization function to set up the object:

var Foo = {
  x: 0,
  y: 0,
  init: function(args) {
    this.x = arguments[0] || 0;
    this.y = arguments[1] || 0;
    return this;  // don't forget to return this!
  }
};
var foo = Object.create(Foo).init(1, 2);

Object creation and initialization can be done in one statement, but the caller is forced to know if init() should be called and if so must remember to call it. Additionally, the implementer of Foo must remember to return this in the init() function for this to work. If the implementer does not return this in init(), the caller needs to call init() in a separate statement:

var Foo = {
  x: 0,
  y: 0,
  init: function(args) {
    this.x = arguments[0] || 0;
    this.y = arguments[1] || 0;
    // return undefined, not `this'
  }
};
var foo = Object.create(Foo);
foo.init(1, 2);

With Initialize.js, objects can be created and initialized with one statement, and the caller does not have to remember to call init(). Additionally, the return value of init() is ignored, so the implementer does not have to remember to return this.

var Foo = {
  x: 0,
  y: 0,
  init: function(args) {
    this.x = arguments[0] || 0;
    this.y = arguments[1] || 0;
    // works with any return value
  }
};
var foo = Init.create(Foo, 1, 2);