ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with arrays
As a result of its restrictions, a Vector has three primary benefits over an Array instance whose elements are all
instances of a single class:
Performance: array element access and iteration are much faster when using a Vector instance than when using an
Array instance.
Type safety: in strict mode the compiler can identify data type errors. Examples of such errors include assigning a
value of the incorrect data type to a Vector or expecting the wrong data type when reading a value from a Vector.
At run time, data types are also checked when adding data to or reading data from a Vector object. Note, however,
that when you use the push() method or unshift() method to add values to a Vector, the arguments’ data types
are not checked at compile time. When using those methods the values are still checked at run time.
Reliability: runtime range checking (or fixed-length checking) increases reliability significantly over Arrays.
Aside from the additional restrictions and benefits, the Vector class is very much like the Array class. The properties
and methods of a Vector object are similar—for the most part identical—to the properties and methods of an Array.
In most situations where you would use an Array in which all the elements have the same data type, a Vector instance
is preferable.
Creating arrays
Flash Player 9 and later, Adobe AIR 1.0 and later
You can use several techniques to create an Array instance or a Vector instance. However, the techniques to create each
type of array are somewhat different.
Creating an Array instance
Flash Player 9 and later, Adobe AIR 1.0 and later
You create an Array object by calling the Array() constructor or by using Array literal syntax.
The Array() constructor function can be used in three ways. First, if you call the constructor with no arguments, you
get an empty array. You can use the length property of the Array class to verify that the array has no elements. For
example, the following code calls the Array() constructor with no arguments:
var names:Array = new Array();
trace(names.length); // output: 0
Second, if you use a number as the only parameter to the Array() constructor, an array of that length is created, with
each element’s value set to undefined. The argument must be an unsigned integer between the values 0 and
4,294,967,295. For example, the following code calls the Array() constructor with a single numeric argument:
var names:Array = new Array(3);
trace(names.length); // output: 3
trace(names[0]); // output: undefined
trace(names[1]); // output: undefined
trace(names[2]); // output: undefined
Third, if you call the constructor and pass a list of elements as parameters, an array is created, with elements
corresponding to each of the parameters. The following code passes three arguments to the Array() constructor:
var names:Array = new Array("John", "Jane", "David");
trace(names.length); // output: 3
trace(names[0]); // output: John
trace(names[1]); // output: Jane
trace(names[2]); // output: David
Last updated 6/6/2012
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