Loading mask using AUI/alloy UI

//to Enable the Loading mask write this code in starting of your task
AUI().use( 'aui-loading-mask', function(A){
                         if (A.one('#tagid').loadingmask == null)
                        A.one('#tagid').plug(A.LoadingMask, { background: '#000' });
                            A.one('#tagid').loadingmask.toggle();
                });

//to Disable the loading mask once again call the toggle(); , write this after compleation of your task

AUI().use( 'aui-loading-mask', function(A){

            A.one('#tagid').loadingmask.toggle();
      });

Note : Here #tagid is id of the tag where you want to display loading mask