File Attachment Filter In JavaScript

HTML

<form action="" method="post" enctype="multipart/form-data">
   <input type="file" id="filelocation" name="fileField" onChange="return validateFileExtension(this)">
   <input type="reset">
   <input type="submit" value="Upload"/>
</form>

JS

function validateFileExtension(fld){
   if(!/(\.bmp|\.gif|\.jpg|\.jpeg)$/i.test(fld.value)){
      alert("Invalid image file type.");
      fld.form.reset();
      fld.focus();
      return false;
      }
      return true;
      }
  
function submitfiles(){
      alert("File location --- " +document.getElementById("filelocation").value);
      alert("File name --- " +document.forms[0].elements[0].value);
      }

Example