ActionScript for Flash MX: The Definitive Guide, Second Edition

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Chapter 3: Data and Datatypes

true // Special keyword true identifies this as a Boolean

null // Special keyword null identifies this as the null type

undefined // Special keyword undefined identifies the undefined type

["hello", 2, true] // Square brackets and values separated by commas

// indicate that this is an array

{x: 234, y: 456} // Curly braces and property name/value pairs separated

// by commas indicate that this is an object

As you can see, using correct syntax with data literals is extremely important. Incor-

rect syntax may cause an error or result in the misinterpretation of a datum’s con-

tent. For example:

animal // Missing quotes--animal is interpreted as a variable,

// not a string of text

"1.35" // Numbers in quotes are treated as strings, not numbers

1. 35 // Space before the 3 causes an error

"animal // Missing closing quotation mark causes an error

Automatic Complex Expression Typing

The interpreter computes an expression’s value in order to determine its datatype.

Consider this example:

pointerX = _xmouse;

Because _xmouse stores the location of the mouse pointer as a number, the type of the

expression

_xmouse will always be a number; so, the variable pointerX also becomes a

number.

Usually, the datatype that is automatically determined by the interpreter matches ...