Question

My goal is to use closures while still writing clean code. One thing I noticed is that somehow I always end up repeating myself because one of my anonymous functions is needed in more than one case.

To this goal, I want to have these repeated functions stored in an object which I can later reuse.

Now, to my question. I’ve created this example http://jsfiddle.net/tiagoespinha/tTx64/ and the alert will not fire, because y is null.

However, if I inline the function, everything works fine http://jsfiddle.net/tiagoespinha/tTx64/1/

Is there a trick to work around this? How can I have it working in the first example? The variable y is still there, why can’t JS catch it?

Answer 1

You want objects having own variables (y) and sharing functions.

What you really need is probably prototype.

function Holder() {
   this.y = 5;
   this.myFn();
}
Holder.prototype.myFn = function() {
    alert("The value of the closure var is " + this.y);           
}
new Holder();

I’d suggest the reading of Introduction to Object-Oriented JavaScript so that you don’t try to rebuild OOP with just closures.