Find extension of file in Javascript

In our scripting sometimes we need to upload such documents , at that time there should be a validation for proper file.

For example in your system suppose there is a field for image upload , that is obvious in that field only image formats are allowed (jpg,jpeg,png,gif etc.). At that time you have to give a validation on that field.

In javascript to find the extension and validation here is your code : 

<script type="text/javascript">

      var str = document.form1.file.value.toLowerCase();  

                              // to convert the value in lower case

      var split = str.split(".");    // split the value by "."

      var s =split.length;         // find the length

      var ext = (split[s-1]);    // and then store the extension in variable

      if((ext=='jpg') || (ext=='png') || (ext=='jpeg') || (ext=='gif')  ){ }

      else {
                 alert("Your message for proper input")      ;

                 return false

      }

</script>

enjoy.....