Question

return this.foo("abc",function(){
                           //do something
                      });

Can some one tell me what does the above line do?
THanks

Answer 1

1. It grabs a reference to this, which might be the DOM Window, a DOM element, or any other JavaScript object depending on how and where the above code is being run.
2. It (skipping ahead) prepares a new anonymous Function that //does something.
3. It attempts to invoke a method foo on object this, passing in two parameters "abc" and said anonymous Function.

Very often when you see code that passes along an anonymous function (e.g. function(){ ... }), it is in fact holding on to that function in order to execute it not right away but at some later point in time, such as in response to a click event or a timer.