rails-delegate

Delegation Pattern for JavaScript

This module implements the delegation pattern for JavaScript, in the very popular and usable Rails style.

Delegating methods

delegate = require('rails-delegate');

function Car() {
  this.engine = new Engine();

  delegate('start', 'stop', 'cylinders', { from: this, to: this.engine });
};

myCar = new Car;

Now myCar.start() calls myCar.engine.start() and myCar.stop() calls myCar.engine.stop(). You can also access the property myCar.cylinders, which contains the value of myCar.engine.cylinders.

More information in the spec for delegating methods and properties. This library also provides meaningful error messages.

Delegating Events

You can also forward events emitted by wrapped classes.

function Car() {
  this.engine = new Engine();

  delegateEvents('starting', 'stopping', { from: this.engine, to: this });
};

Now if myCar.engine emits a starting starting event, myCar also emits that event.

Alternatives

This library aims for maximally readable syntax that closely matches the Rails version. There are other libraries that are different and more versatile, for example node-delegates.