Extend `Backbone.Events` with a `debounce` method.

backbone_events_debounce.coffee

# works exactly like `.bind()`, with the difference that it gets executed with a delay.
# Each time the event gets triggered again, the delay gets reset.
# 
# based on: http://benalman.com/projects/jquery-throttle-debounce-plugin/
#
# example:
#
# car = new Backbone.Model
# bind_triggered = debounce_triggered = 0
#
# car.bind 'change', -> bind_triggered++
# car.debounce 'change', 100, -> debounce_triggered++
#
# car.set(ctr: i) for i in [1..3]
# => bind_triggered is 3
# => debounce_triggered is 0. After 0.1 seconds, it will be 1
#

Backbone.Events.debounce = (event, delay, callback) ->
  timeout = 0
  
  debounced = ->
    window.clearTimeout(timeout)
    timeout = window.setTimeout ( -> 
      callback()
      timeout = 0
    ), delay
  
  @bind event, debounced
  

Backbone.Model.prototype.debounce       = Backbone.Events.debounce
Backbone.Collection.prototype.debounce  = Backbone.Events.debounce
Backbone.Router.prototype.debounce      = Backbone.Events.debounce
Backbone.View.prototype.debounce        = Backbone.Events.debounce

backbone_events_debounce.js

Backbone.Events.debounce = function(event, delay, callback) {
  var debounced, timeout;
  timeout = 0;
  debounced = function() {
    window.clearTimeout(timeout);
    return timeout = window.setTimeout((function() {
      callback();
      return timeout = 0;
    }), delay);
  };
  return this.bind(event, debounced);
};

Backbone.Model.prototype.debounce = Backbone.Events.debounce;
Backbone.Collection.prototype.debounce = Backbone.Events.debounce;
Backbone.Router.prototype.debounce = Backbone.Events.debounce;
Backbone.View.prototype.debounce = Backbone.Events.debounce;

Why not use the _.debounce method underscore offers?