Flash CS3 Documentation

Programming ActionScript 3.0 > Working with strings > Basics of strings

Basics of strings

Introduction to working with strings

In programming parlance, a string is a text value--a sequence of letters, numbers, or other characters strung together into a single value. For instance, this line of code creates a variable with the data type String and assigns a literal string value to that variable:

var albumName:String = "Three for the money";

As this example shows, in ActionScript you can denote a string value by surrounding text with double or single quotation marks. Here are several more examples of strings:

"Hello"
"555-7649"
"http://www.adobe.com/"

Any time you manipulate a piece of text in ActionScript, you are working with a string value. The ActionScript String class is the data type you can use to work with text values. String instances are frequently used for properties, method parameters, and so forth in many other ActionScript classes.

Common tasks for working with strings

The following are common string-related tasks that are explored in this chapter:

• Creating String objects
• Working with special characters such as carriage-return, tab, and non-keyboard characters
• Measuring string length
• Isolating individual characters in a string
• Joining strings
• Comparing strings
• Finding, extracting, and replacing portions of a string
• Making strings uppercase or lowercase

Important concepts and terms

The following reference list contains important terms that you will encounter in this chapter:

• ASCII: A system for representing text characters and symbols in computer programs. The ASCII system supports the 26-letter English alphabet, plus a limited set of additional characters.
• Character: The smallest unit of text data (a single letter or symbol).
• Concatenation: Joining multiple string values together by adding one to the end of the other, creating a new string value.
• Empty string: A string that contains no text, white space, or other characters, written as "". An empty string value is different from a String variable with a null value--a null String variable is a variable that does not have a String instance assigned to it, whereas an empty string has an instance with a value that contains no characters.
• String: A textual value (sequence of characters).
• String literal (or "literal string"): A string value written explicitly in code, written as a text value surrounded by double quotation marks or single quotation marks.
• Substring: A string that is a portion of another string.
• Unicode: A standard system for representing text characters and symbols in computer programs. The Unicode system allows for the use of any character in any writing system.

Working through in-chapter examples

As you're working through the chapter, you may want to test some of the example code listings for yourself. Because the code listings in this chapter deal primarily with manipulating text, testing the examples will involve viewing the values of the variables used in the examples, either by writing values into a text field instance on the Stage or by using the trace() function to print values to the Output panel. These techniques are described in detail in Testing in-chapter example code listings.

Flash CS3