Methods for using regular expressions with strings

Flash Player 9 and later, Adobe AIR 1.0 and later

The RegExp class includes two methods: exec() and test().

In addition to the exec() and test() methods of the RegExp class, the String class includes the following methods that let you match regular expressions in strings: match(), replace(), search(), and splice().

The test() method

The test() method of the RegExp class simply checks the supplied string to see if it contains a match for the regular expression, as the following example shows:

var pattern:RegExp = /Class-\w/; 
var str = "Class-A"; 
trace(pattern.test(str)); // output: true

The exec() method

The exec() method of the RegExp class checks the supplied string for a match of the regular expression and returns an array with the following:

  • The matching substring

  • Substring matches for any parenthetical groups in the regular expression

The array also includes an index property, indicating the index position of the start of the substring match.

For example, consider the following code:

var pattern:RegExp = /\d{3}\-\d{3}-\d{4}/; //U.S phone number 
var str:String = "phone: 415-555-1212"; 
var result:Array = pattern.exec(str); 
trace(result.index, " - ", result); 
// 7-415-555-1212

Use the exec() method multiple times to match multiple substrings when the g (global) flag is set for the regular expression:

var pattern:RegExp = /\w*sh\w*/gi; 
var str:String = "She sells seashells by the seashore"; 
var result:Array = pattern.exec(str); 
     
while (result != null) 
{ 
    trace(result.index, "\t", pattern.lastIndex, "\t", result); 
    result = pattern.exec(str); 
} 
//output:  
// 0      3      She 
// 10      19      seashells 
// 27      35      seashore

String methods that use RegExp parameters

The following methods of the String class take regular expressions as parameters: match(), replace(), search(), and split(). For more information on these methods, see Finding patterns in strings and replacing substrings.