upload edilen dosyanın uzantısını öğrenme

<div id="uploadform">  <script> 
  function send() { 
  javascript: location = 'upload.asp?hqtp=sent';     
  } 
  </script> 
   
   
              <h3><span>SEND YOUR PHOTO</span></h3> 
              <fieldset><legend>Send Your Photo</legend> 
              <p class="first"> 
                      <input placeholder="Write Your Name" type="text" name="name" id="name" size="30" /> 
                  </p> 
                  <p> 
                      <input placeholder="Write Your Email" type="text" name="email" id="email" size="30" /> 
                  </p> 
                  <p> 
                      <input placeholder="Write Photo's Country" type="text" name="country" id="country" size="30" /> 
              </p>     
                  <p> 
                    <input placeholder="Write Photo's City" type="text" name="city" id="city" size="30" /> 
                  </p> 
                  <p> 
                    <button id="choosebutton" onClick="document.querySelector('input#button22').click()">CHOOSE A PHOTO</button> 
  <input id="button22" style="visibility: collapse; width: 0px;" type="file" onChange="upload(this.files[0])"> 
                    </p> 
  <script> 
    
      window.ondragover = function(e) {e.preventDefault()} 
      window.ondrop = function(e) {e.preventDefault(); upload(e.dataTransfer.files[0]); } 
      function upload(file) { 
    
          if (!file || !file.type.match(/image.*/)) return; 
    
          document.body.className = "uploading"; 
    
          /* Lets build a FormData object*/ 
          var fd = new FormData(); // I wrote about it:https://hacks.mozilla.org/2011/01/how-to-develop-a-html5-image-uploader/ 
          fd.append("image", file); // Append the file 
          fd.append("key", "6528448c258cff474ca9701c5bab6927"); // Get your own keyhttp://api.imgur.com/ 
          var xhr = new XMLHttpRequest(); // Create the XHR (Cross-Domain XHR FTW!!!) Thank you sooooo much imgur.com 
          xhr.open("POST", "http://api.imgur.com/2/upload.json"); // Boooom! 
          xhr.onload = function() { 
              // Big win! 
              document.querySelector("#link").value = JSON.parse(xhr.responseText).upload.links.imgur_page; 
              document.body.className = "uploaded"; 
          } 
          
          xhr.send(fd); 
      } 
  </script> 
  <style> 
      #link, #uploadingbarr , #uploadbutton1 {display: none} 
      #uploadbutton1 {display: inline-block;} 
      .uploading #uploadingbarr {display: inline} 
      .uploaded #link {display: inline} 
  </style> 
  <p id="uploadingbarr"><img src="http://forum.ceviz.net/images/uploading.gif" /></p> 
  <input name="resimurl" readonly="readonly" type="text" id="link" size="35" > 
                  <p class="submit"><button id="sendbutton" onClick="send();" type="submit">Send Your Photo</button></p>                     
              </fieldset>                                     
   </div>