Learning the hard way

I have come acrooss some rare occasions in programming in which the language/environment/common sense really wants you to learn after literally breaking you head. Thats what happened today in a javascript app I am doing (Shh! Its still a secret). For 2 days I have been trying to use everything I know to clean up a problem I was having with every node firing the event when only one should've been. That was until I realised it was due to this small error hiding in the corner.

window.addEventListener instead of this.addEventListener

So note to self, PAY ATTENTION