Webform Redirect Hook
You can disable the double click  on submit using the below jQuery code.

$('#formid').submit(function(){
    $(this).children('input[type=submit]').prop('disabled', true);
});


Now you can use the below code to alter submit of webform in your custom module

/**
 * Implementation of hook_form_alter().
 */
function mywebform_extra_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  // Add extra submit for a particular Webform node:
  if ($form_id == 'webform_client_form_44') {


    // Add the submit handler after the existing Webform submit handler,
    // but before the second Webform handler. Pop off the first one and add
    // ours second.
   $form['#submit'][] = 'mywebform_extra_validate_44';
  }
}

/**
 * Submit handler for Webform ID #44.
 */
function mywebform_extra_submit_44(&amp;$form, &amp;$form_state) {
  global $user;


  // Now you can perform here api request and redirect 
}


Hope it will help you.