User Guide

302 Using Regular Expressions

The lastIndex property

The lastIndex property specifies the index position in the string at which to start the next

search. This property affects the

exec() and test() methods called on a regular expression

that has the

g flag set to true. For example, consider the following code:

var pattern:RegExp = /p\w*/gi;

var str:String = "Pedro Piper picked a peck of pickled peppers.";

trace(pattern.lastIndex);

var result:Object = pattern.exec(str);

while (result != null)

{

trace(pattern.lastIndex);

result = pattern.exec(str);

}

The lastIndex property is set to 0 by default (to start searches at the beginning of the string).

After each match, it is set to the index position following the match. Therefore, the output for

the preceding code is the following:

If the global flag is set to false, the exec() and test() methods do not use or set the

lastIndex property.

The

match(), replace(), and search() methods of the String class start all searches from

the beginning of the string, regardless of the setting of the

lastIndex property of the regular

expression used in the call to the method. (However, the

match() method does set

lastIndex to 0.)

You can set the

lastIndex property to adjust the starting position in the string for regular

expression matching.

The source property

The source property specifies the string that defines the pattern portion of a regular

expression. For example:

var pattern:RegExp = /foo/gi;

trace(pattern.source); // foo