[Nutrox]

 
Array mapping can come in very useful sometimes. What array mapping basically does is pass each array value to a function, and that function can then either alter the array value or return a result based on the array value.

I have included a prototype function and a standard function here just in case you prefer a particular flava.

You setup the Array prototype method like this:

Array.prototype.map = function(callback)
{
    var a = [];
    var n = this.length;
    while (n--)
    {
        a[n] = callback(this, n, this[n]);
    }
    return a;
} 

Prototype Example 1
This example checks to see which values in the myNumbers array are greater than 3. The results (in this example true or false) will be returned in an array.

var myNumbers = [1, 2, 3, 4, 5, 6];
var results   = myNumbers.map(checkNumbers);
 
trace( results ); // false, false, false, true, true, true
 
//
 
function checkNumbers(array, index, value)
{
    // Check if the value is greater than 3.
    return value > 3;
} 

Prototype Example 2
This example will prefix each value in the myNames array with "Name: ".

var myNames = ["Andy", "Bob", "Charlie", "Dood"];
var newNames = myNames.map(changeNames);
 
trace( newNames ); // Name: Andy, Name: Bob, Name: Charlie, Name: Dood
 
//
 
function changeNames(array, index, value)
{
    return "Name: " + value;
} 

Better Example 1
We have left the world of prototypes now. This is the same example as Prototype Example 1 but instead of using a prototype a standalone function is used for the array mapping.

function mapArray(array:Array, callback:Function):Array
{
    var a:Array = [];
    var n:Number = array.length;
    while (n--)
    {
        a[n] = callback(array, n, array[n]);
    }
    return a;
}
 
//
 
var myNumbers:Array = [1, 2, 3, 4, 5, 6];
var results:Array   = mapArray(myNumbers, checkNumbers);
 
trace( results ); // false, false, false, true, true, true
 
//
 
function checkNumbers(array:Array, index:Number, value):Array
{
    return value > 3;
} 

PS: Array mapping is built-in to the AS3 Array class, so these examples are only useful for AS1 / AS2.