Question

Am experimenting with an anonymous function :

var a:Object = new Object() ;
a.b = new Function()

a.b =function()
{
    trace("hello");
}

trace(a.b())

Output :
hello
undefined

What’s undefined ??

Answer 1

You have two trace statements running:

trace("hello");

trace(a.b());

When you call trace(a.b()) first a.b() is called. a.b is simply this function:

function()
{
    trace("hello");
}

So that runs and outputs “hello”.

Now the second trace (trace(a.b()) tries to output the result of a.b(). The problem is that you do not return anything in a.b(), so the result is undefined.

Edit: As JonatanHedborg points out in his comment, the line a.b = new Function() is really not needed as you overwrite it on the next line.

If you change this to:

var a:Object = new Object() ;

a.b = function()
{
    return "Hello";
}

trace(a.b())

You should now see “hello” as the output.

Alternatively, if you change it to this:

var a:Object = new Object() ;

a.b = function()
{
    trace("hello");
}

trace(a.b)

so that you are tracing the value of a.b instead of the value of the result of a.b() then you should see “hello” and “Function function” (or something similar) as the result.