JavaScript - RegExp lastIndex Property


Advertisements


Description

lastIndex 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 property allows you to call those methods repeatedly, to loop through all matches in a string and works only if the "g" modifier is set.

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 the lastIndex to 0 when they fail to find a match (or another match).

Syntax

Its syntax is as follows −

RegExpObject.lastIndex

Return Value

Returns an integer that specifies the character position immediately following the last match.

Example

Try the following example program.

<html>
   
   <head>
      <title>JavaScript RegExp lastIndex Property</title>
   </head>
   
   <body>
      
      <script type="text/javascript">
         var str = "Javascript is an interesting scripting language";
         var re = new RegExp( "script", "g" );
         
         re.test(str);
         document.write("Test 1 - Current Index: " +  re.lastIndex); 
         
         re.test(str);
         document.write("<br />Test 2 - Current Index: " + re.lastIndex); 
      </script>
      
   </body>
</html>

Output

Test 1 - Current Index: 10
Test 2 - Current Index: 35 

javascript_regexp_object.htm