jQuery plugin to notify users if they close the page, and there are still some Ajax requests pending.

jquery.onclose.coffee

$ = jQuery

TRANSFORM_TYPES = ['PUT', 'POST', 'DELETE']

$.activeTransforms = 0

$(document).ajaxSend (e, xhr, settings) ->
  return unless settings.type in TRANSFORM_TYPES
  $.activeTransforms += 1

$(document).ajaxComplete (e, xhr, settings) ->
  return unless settings.type in TRANSFORM_TYPES
  $.activeTransforms -= 1

window.onbeforeunload or= ->
  if $.activeTransforms
    '''There are some pending network requests which
       means closing the page may lose unsaved data.'''

jquery.onclose.js

(function(){
  var $ = jQuery;

  var TRANSFORM_TYPES = ['PUT', 'POST', 'DELETE'];

  $.activeTransforms = 0;

  $(document).ajaxSend(function(e, xhr, settings) {
    if (TRANSFORM_TYPES.indexOf.call(settings.type) < 0) return;
    return $.activeTransforms += 1;
  });

  $(document).ajaxComplete(function(e, xhr, settings) {
    if (TRANSFORM_TYPES.indexOf.call(settings.type) < 0) return;
    return $.activeTransforms -= 1;
  });

  window.onbeforeunload || (window.onbeforeunload = function() {
    if ($.activeTransforms) {
      return 'There are some pending network requests which\nmeans closing the page may lose unsaved data.';
    }
  });
}).call(this);