ActionScript for Flash MX: The Definitive Guide, Second Edition

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Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 3: Data and Datatypes

Converting to a Boolean

When we want to convert a datum to a Boolean, we can use the global Boolean()

function, which uses similar syntax to the String() and Number() functions. For

example:

Boolean(5); // The result is true

Boolean(x); // Converts value of x to a Boolean

Don’t confuse the global Boolean() function with the built-in class constructor of the

same name. Both are described in the Language Reference.

Conversion Duration

All type conversions performed on variables, array elements, and object properties

are temporary unless the conversion happens as part of an assignment. Here we see a

temporary conversion:

var x = "10"; // x is a string.

y = x - 5; // y is now 5; x's value was temporarily converted to a number.

trace(typeof x); // Displays: "string"; the conversion was temporary because

// it occurred incidentally while evaluating an expression.

Here we see a permanent conversion that is the result of an assignment:

x = "10"; // x is a string.

x = x - 5; // x is converted permanently to a number.

trace(typeof x); // Displays: "number"; the conversion was permanent because

// it occurred as part of an assignment.

Determining the Type of an Existing Datum

To determine what kind of data is held in a given expression before, say, proceeding

with a section ...