jQuery form input helper text function

We started using jQuery at work a few months ago and we began to analyze the JavaScript we were writing. We found that we were using some code over and over and one was a few lines that handled adding some helper text to an input on page load and removing it when a user clicks the input to type some text. It also handles when a form is submitted removing the helper text before it is sent to the server for processing (no server side checks for the helper text).

Here is the code for a universal function in handling form input helper text. The last value will default to 'default'. This was a class name we chose to allow us to lighten the color of the helper text only.

/**
* Handles add/removing helper text for form input fields
*
* @param selector   Jquery selector value of element to add helper to
* @param helperText Text to be placed in the input if input has no value
* @param css        Css class to be added when helper text is set
*/
function form_helper_text( selector, helperText, css ) {
   $(document).ready(function(){
       // set css default value if none provided
       css = typeof( css ) != 'undefined' ? css : 'default';
      
       // select form element and if helper text is submitted replace with ''
       var form = $( selector ).parents( 'form:first' );
       $( form ).submit(function(){
           if( $( selector ).val() == helperText ) {
               $( selector ).val( '' );
           }
       });

       // set action when field is not selected (add helper text)
       $( selector ).blur(function(){
           if( $(this).val() == '' ) {
               $(this).addClass( css );
               $(this).val( helperText );
           }
       });

       // set action when field is selected (remove helper text)
       $( selector ).focus(function(){
           if( $(this).val() == helperText ) {
               $(this).val( '' );
               $(this).removeClass( css );
           }
       });

       // trigger blue action to add helper text
       $( selector ).trigger( 'blur' );
   });
}