JavaScript: The Definitive Guide, Fourth Edition

Name

RegExp.lastIndex — the starting position of the next match

Availability

JavaScript 1.2; JScript 5.5; ECMAScript v3

Synopsis

                  regexp.lastIndex

Description

lastIndex is a read/write property of RegExp objects. For regular expressions with the g attribute set, it contains an integer that specifies the character position immediately following the last match found by the RegExp.exec( ) and RegExp.test( ) methods. These methods use this property as the starting point for the next search they conduct. This allows you to call those methods repeatedly, to loop through all matches in a string. Note that lastIndex is not used by RegExp objects that do not have the g attribute and do not represent global patterns.

This property is read/write, so you can set it at any time to specify where in the target string the next search should begin. exec( ) and test( ) automatically reset lastIndex to 0 when they fail to find a match (or another match). If you begin to search a new string after a successful match of some other string, you have to explicitly set this property to 0.

See Also

RegExp.exec( ), RegExp.test( )