Question

EDITED

What is the difference in doing:

var a = function(){};
a.myProperty = function(){};

Versus:

var a = function(){};
a.prototype.myProperty = function(){};

I realise this might be a silly or vague question but what do I need to understand to know the difference between the two and when to use one over the other?

Answer 1

Note that the question has been heavily edited since it was first posed, which is why the existing comment and answer make no sense.

All functions have prototypes. The methods attached to these prototypes are available to instances of objects created by calling the function as a constructor. So in the second example, if you write var o = new a(); then you will be able to invoke o.myProperty();.

Additionally all functions are objects, so you can set arbitrary properties directly on the function itself, as per the first example. You can also access the function from the object using o.constructor (or this.constructor from a member function). This could be used to implement the equivalent of C++ static class variables.