Flash, Flex and ActionScript tutorials – flashadvanced

This article will show you a collection of optimization tips for ActionScrip 3 that you can use to speed up your application’s performance.

Let’s begin with the first rule in AS 3 optimization tehniques:

1. Use integers for iterations. Int type performs faster than Number when looping through the items of an array. This is because array indexing is faster with ints.

for(var i:int = 0; i < 1000000; i++);

2. Use shorthand operators whenever possible

Incrementing is faster using the "++" operator than using "i = i + 1". It is the same situation with "a += b" which is faster than "a = a + b";

3. Use multiplication instead of division when dividing by 2.

In this case it is better to use multiplication with .5 than division by 2.

Slow:

var a:Number = b / 2;

Fast:

var a:Number = b*.5;

4. Use bitwise shift operators for even faster performance.

Slow:

var a:int = 10;
a = a * 2; //returns 20
a = a * 4; //returns 40
a = a / 2; //returns 5;

Fast:

var a:int = 10;
a = a << 1; //returns 20
a = a << 2; //returns 40
a = a >> 1; //returns 5

5. Use single line variable declaration

Slow:

var a:int = 1;
var b:int = 2;
var c:int = 3;

Fast:

First use the "var" keyword and then declare the variables on a single line.

var a:int = 1, b:int = 2, c:int = 3;

6. Use "null" intead of "try .. catch" if possible:

var myArray:Array;
if(myArray != null)
	myArray.pop();
else
	trace("its null");

is way faster than:

try{
	myArray.pop();
}catch(e:Error){
	trace(e.message);
}

7.Use int(a) instead of Math.floor(a). Math.floor(a) is 10 times slower than int(a).
Slow:

for(var i:int=0; i<1000000; i++){
	var a:int = Math.floor(1.5);
}

Fast:

for(var i:int=0; i<1000000; i++){
	var a:int = int(1.5);
}

This is how you can test your code performance:

for(var i:int=0; i<1000000; i++){
	var a:int = 4 << 1;
	var b:int = 4 << 2;
	var c:int = 4 >> 1;
}
trace(getTimer());