ActionScript for Flash MX: The Definitive Guide, Second Edition

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

Working with Strings

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103

Character Code Functions

In “Unicode escape sequences,” we saw how to insert characters into a string using

escape sequences. ActionScript also includes two built-in functions for working with

character code points in strings: fromCharCode() and charCodeAt().

Example 4-4. Character case animation

// Add a new caseAni( ) method to the built-in TextField class.

TextField.prototype.caseAni = function (msg) {

// Store a reference to the current text field in tf. We'll need to

// access it from the nested function moveUppercaseLetter( ).

var tf = this;

tf.upperIndex = 0; // The current location of the uppercase letter.

tf.msg = msg; // The message to animate.

// Start the animation running by calling

// the moveUppercaseLetter( ) function every 100 milliseconds.

var id = setInterval(moveUppercaseLetter, 100);

// Define the nested moveUppercaseLetter( ) function. Here's where we do

// all our string manipulation.

function moveUppercaseLetter ( ) {

// Chop the msg string into three pieces and make the middle one uppercase.

var part1 = tf.msg.slice(0, tf.upperIndex);

var part2 = tf.msg.charAt(tf.upperIndex);

var part2 = part2.toUpperCase( );

var part3 = tf.msg.slice(tf.upperIndex+1, tf.msg.length);

tf.msg = part1 + part2 + part3;

// Display the formatted msg ...