vjs.one() event listening cannot be turned off with vjs.off()

[delner]

Binding an event handler using one() cannot be removed using off().

Scenario:

var callback = new function() { alert('Do not trigger me!') };
var component = new Component(); // Any CoreObject has the one/off functions
component.one('myEvent', callback);
component.off('myEvent', callback);

component.trigger('myEvent'); // Should not raise alert, but will anyways.

Cause

The vjs.one() function wraps the function passed with an anonymous function:

vjs.one = function(elem, type, fn) {
  vjs.on(elem, type, function(){
    vjs.off(elem, type, arguments.callee);
    fn.apply(this, arguments);
  });
};

When vjs.on() is called, it adds a guid to the function, so it can identify and remove it later. When vjs.off() is called, it seeks the function with that guid and removes it. Because callback in my example gets wrapped with an anonymous function, it does not assign the guid to callback, rather to the anonymous function. When vjs.off(callback) is called, it doesn't find a matching guid and thus fails to unbind the event handler.

Proposed Solution

"Sync" the guid on the anonymous function and fn, so they both have the same guid. This will allow event handlers set with vjs.one() to be 'cancelled.'

Sample code:

vjs.one = function(elem, type, fn) {
  var func = function(){
    vjs.off(elem, type, arguments.callee);
    fn.apply(this, arguments);
  };

  // If on() is called before one() is
  // Inherit the ID of fn, so that one() may be cancelled.
  if(fn.guid) { func.guid = fn.guid; }

  vjs.on(elem, type, func); // This function will set func.guid if it wasn't previously set.

  // If one() is called before on()
  // Set the ID of fn, so that on() may be cancelled.
  if(!fn.guid) { fn.guid = func.guid; }
};

This code works on my fork.

[heff]

Thanks for the find + fix. Could probably be simplified like so.

func.guid = fn.guid = fn.guid || vjs.guid++;

The bind() inside on() will keep an existing guid.

Want to do a pull request and get credit?

[delner]

Sure thing, I'll set it up.