Javascript scope addEventListener and this

Question

I am a C# developer experimenting with JavaScript and I\'m trying to get my head around the scope :)

I have the following code which contains an addEventListe

Answer 1

Keyboard.prototype.listen = function() {
    var self = this;
    window.addEventListener('keydown', function(event) {
       self.handle_keydown(event);
       // self is your Keyboard object. You can refer to all your properties from this
    });
}

How this code works:

1. We are creating variable self, which stores reference to this variable.
2. The inner function is a closure, hence it has reference to self.
3. When the closure function is called: this points to the dom object, while self points to keyboard object.
4. The closure is called with event as a parameter that we pass on to the member function of the keyboard object.