Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <head> <script src="../../ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"> </script> <script> $(document).ready(function(){ $("button").click(function(){ $("li").toggleClass(function(n){ return "listitem_" + n; }); }); }); </script> <style> .listitem_1, .listitem_3 { color:red; } .listitem_0, .listitem_2 { color:blue; } </style> </head> <body> <h1>This is a heading</h1> <ul> <li>Peter</li> <li>Lois</li> <li>Chris</li> <li>Stewie</li> </ul> <button>Add/remove classes to list items</button> </body> </html>
Result:
W3Schools.com - Try it yourself