How to determine if a function has been called without setting global variable

Question

I am looking for a good technique to get away from what I am tempted to do: to set a global variable.

The first time someone runs a function by clicking a button it

Answer 1

What you could do is unhook the init function from the prototype.

​var Obj = function () {
    this.init = function () {
        document.write("init called
");
        this.init = null;
    }
}
var o = new Obj();
if (o.init) document.write("exists!
");
o.init();
if (o.init) document.write("exists!
");
o.init();

​ The first if will be true and print exists! but since the function removes itself, the second if will fail. In my example, I call the second init unconditionally just to show that nothing will happen, but of course you could call it only if it exists:

if (o.init) o.init();

http://jsfiddle.net/coreyog/Wd3Q2/