How to clear cookie with cookie name on from submit? When users fill values in node form input fields I set cookies of those values with help of javascript code, example : 

    var date = new Date();
    date.setTime(date.getTime() + (60 * 60 * 1000));

 $('#edit-field-topic-und').on('change', function() {
            var section =  $(this).find("option:selected").val();
            console.log(section);
            if(section){
                $.cookie("section", section, { expires: date });
            }
        })

        $('#edit-field-topic2-und').on("change", function () {
            var topic = $(this).val();
            console.log(topic);
            if(topic){
                $.cookie("topic", topic, { expires: date });
            }
        });

        $('#edit-field-language-und').on('change', function() {
            var language =  $(this).find("option:selected").val();
            console.log(language);
            if(language){
                $.cookie("language", language, { expires: date });
            }
        })


If user does not submits from and next time come to node add form page, I set default values in from with help of form alter: 

case 'link_node_form':
      /*show default values from cookie*/
      if (empty($form['nid']['#value'])) {



        if(isset($_COOKIE['section'])) {
          $form['field_topic']['und']['#default_value'] = $_COOKIE['section'];
        }

        if(isset($_COOKIE['topic'])) {
          $form['field_topic2']['und']['#default_value'] = $_COOKIE['topic'] ;
        }

        if(isset($_COOKIE['language'])) {
          $form['field_language']['und']['#default_value'] = $_COOKIE['language'];
        }


      // clear cookies after from submit
        $form['#submit'][] = 'custom_overrides_link_node_form_submit';


      }


Now when user submit form and node got created successfully cookie is not clearing or the cookies got values of last submitted node.

Please suggest how to clear / unset cookies when form get submitted.

function custom_overrides_link_node_form_submit($form, &amp;$form_state) {



  if(isset($_COOKIE['section'])) {

    unset($_COOKIE['section']);
  }

  if(isset($_COOKIE['topic'])) {

    unset($_COOKIE['topic']);
  }

  if(isset($_COOKIE['language'])) {

    unset($_COOKIE['language']);
  }


}
By setting it to one hour ago time with empty value I managed to make it working according to my requirements. 

function custom_overrides_link_node_form_submit($form, &amp;$form_state) {



  if(isset($_COOKIE['section'])) {

    unset($_COOKIE['section']);
    setcookie("section", '', time() - 3600);
  }

  if(isset($_COOKIE['topic'])) {

    unset($_COOKIE['topic']);
     setcookie("topic", '', time() - 3600);
  }

  if(isset($_COOKIE['language'])) {
     unset($_COOKIE['language']);
     setcookie("language", '', time() - 3600);
  }


}