code: function mouseLeftWindow(fn) {
          function handler(event) {
              var from = event.relatedTarget || event.toElement;
              if (!from || from.nodeName === 'HTML') {
                  fn(event);
              }
          }
  
          document.addEventListener('mouseout', handler, false);
  
          return {
              destroy: function destroy() {
                  document.removeEventListener('mouseout', handler);
              }
          };
      }
docs: /*
  Fader