title: jquery append' called on an object
body: <p>Why do i get the follow error from my browser:</p>
  
  <p>TypeError: 'append' called on an object that does not implement interface FormData.</p>
  
  <p>?</p>
  
  <p>how can i fix it?</p>
  
  <p>MY Jquery code</p>
  
  <pre><code>$(document).on("click", ".edit_save-btn", function(e){
  
      e.preventDefault();
  
      var form = $(this).closest('form')[0]; 
      for (i = 0; i &lt; form.elements.length; i++) 
      {
          if (form.elements[i].type == 'file') 
          {
              if (form.elements[i].value == '') {
                  form.elements[i].parentNode.removeChild(form.elements[i]);
              }
          }
      }
  
  
  
      var form_data = new FormData(form);
      var act = "edit";
  
  
      form_data.append('agntID', "4");
      form_data.append('act', 'edit');
  
  //  form_data.push({name: 'agntID', value: "4"});   
  //  form_data.push({name: 'act', value: 'edit'});   
      }); 
  </code></pre>
  
  <p>HTML</p>
  
  <pre><code>&lt;form action="#" method="post" enctype="multipart/form-data" id="4" class="item"&gt;
  
      &lt;div class="col-md-2 item_logo"&gt;&lt;input name="file[]" type="file"&gt;&lt;/div&gt;
      &lt;div class="col-md-2 item_name"&gt;&lt;input name="agnt[name]" value="Agency 2" type="text"&gt;&lt;span&gt;*&lt;/span&gt;&lt;/div&gt;
      &lt;div class="col-md-2 item_mainEmail"&gt;&lt;input name="agnt[mainEmail]" value="email@gmail.com" type="text"&gt;&lt;/div&gt;
      &lt;div class="col-md-2 item_contact"&gt;&lt;textarea type="text" name="agnt[contact]"&gt;some details&lt;/textarea&gt;&lt;/div&gt;
      &lt;div class="col-md-2 panel-menu"&gt;
          &lt;span class="edit_msg"&gt;&lt;/span&gt;
  
          &lt;i class="fa fa-refresh fa-spin fa-2x fa-fw edit_form-loader"&gt;&lt;/i&gt;
          &lt;a href="#" class="btn btn-success edit_save-btn"&gt;Save&lt;/a&gt;
  
      &lt;/div&gt;
  
  &lt;/form&gt;
  </code></pre>
  
  <p>............ ..........................</p>