Question

If I have a JavaScript constructor function, and I set a destroy method on its prototype. Is it possible to delete (or at least unset) the instance from the destroy method? Here’s an example of what I’m trying to do.

Klass.prototype = {
  init: function() {
    // do stuff
  },
  destroy: function() {
    // delete the instance    
  }
};

k = new Klass
k.destroy()
console.log(k) // I want this to be undefined

I understand that I can’t simply do this = undefined from with the destroy method, but I thought I could get around that by using a timeout like so:

destroy: function() {
  var self = this;
  setTimeout( function() {
    self = undefined
  }, 0)  
}

I thought the timeout function would have access to the instance via self from the closure (and it does), but that doesn’t seem to work. If I console.log(self) from inside that function it shows up as undefined, but k in the global scope is still an instance of Klass.

Does anyone know how to make this work?

Answer 1

k is a reference that points out to an instance of Klass. when you call destroy as a method of Klass the this inside the function gets bound to the object you called a destroy method on. It now is another reference to that instance of Klass. The self that you close on in that little closure is yet another reference to that instance. When you set it to undefined you clear that reference, not the instance behind it. You can’t really destroy that instance per se. You can forget about it (set all the references to undefined and you won’t find it again) but that is as far as you can go.

That said, tell us what you want to accomplish with this and we’ll be glad to help you find a solution.