How can this be the output? - actionscript-3

Question

It is simple program, but the output of the program is so unexpected .
Programming language : ActionScript 3.0

Answer 1

So, we have 3 kinds of syntax:
// 1. Variable declaration.
var a:int;
// 2. Assign value to variable.
a = 0;
// 3. Declare variable and assign value in one go.
var b:int = 1;
The tricky moment is that in AS3 variable declaration is NOT an operation. It is a construction that tells compiler you are going to use a variable with a certain name and type within a given context (as a class member or as a timeline variable or as a local variable inside a method). It literally does not matter where in the code you declare your variables. AS3 is, I must admit, ugly from this very perspective. The following code might look weird yet it is syntactically correct. Lets read and understand what it does and why.
// As long as they are declared anywhere,
// you can access these wherever you want.
i = 0;
a = 0;
b = -1;
// The 'for' loop allows a single variable declaration
// within its parentheses. It is not mandatory that
// declared variable is an actual loop iterator.
for (var a:int; i <= 10; i++)
{
// Will trace lines of 0 0 -1 then 1 1 0 then 2 2 1 and so on.
trace(a, i, b);
// You can declare a variable inside the loop, why not?
// The only thing that actually matters is that you assign
// the 'a' value to it before you increment the 'a' variable,
// so the 'b' variable will always be one step behind the 'a'.
var b:int = a;
a++;
}
// Variable declaration. You can actually put
// those even after the 'return' statement.
var i:int;
Let me say it again. The place where you declare your variables does not matter, just the fact you do at all. Declaring variable is not an operation. However, assigning a value is. Your code actually goes as following:
function bringMe(e:Event):void
{
// Lets explicitly declare variables so that assigning
// operations will come out into the open.
var i:int;
var score:int;
for (i = 1; i <= 10; i++)
{
// Without the confusing declaration it is
// obvious now what's going on here.
score = 0;
score++;
// Always outputs 1.
trace(score);
// Outputs values from 1 to 10 inclusive, as expected.
trace(i);
}
}