Simple Form Validation with Prototype

1:  <script src="prototype.js"></script>  
2:  <script>  
3:    //example: checkForm('myForm');  
4:    function checkForm(frm)  
5:    {  
6:      allFields = Form.getElements("myForm");  
7:      for(i=0;i<allFields.length;i++)  
8:      {  
9:        if(allFields[i].value == "")  
10:        {  
11:          $(allFields[i]).addClassName('error');  
12:        } else {  
13:          $(allFields[i]).removeClassName('error')  
14:        }  
15:      }  
16:    }  
17:  </script>