Convert text to uppercase

Convert text to uppercase

I found this script on the internet but it doesn't seem to work in my webpage.
  1. $('jqueryselector').val($(this).val().toUpperCase());

What am I missing?

I get the following error:

SCRIPT5007: Unable to get value of the property 'toLowerCase': object is null or undefined 
jquery.tools.min.js, line 1 character 25784

I'm not even sure why I am getting a 'toLowerCase' error when I'm using the toUpperCase function??

So confused!