code: function ( e ) {
  
          var i = R.ui.length, next = -1, u, x, y;
  
          while( i-- ){
  
              u = R.ui[i];
  
              if( u.isCanvasOnly ) {
  
                  x = u.mouse.x;
                  y = u.mouse.y;
  
              } else {
  
                  x = e.clientX;
                  y = e.clientY;
  
              }
  
              if( R.onZone( u, x, y ) ){ 
                  
                  next = i;
                  
                  if( next !== R.current ){
                      R.clearOldID();
                      R.current = next;
                      R.ID = u;
                  }
                  break;
              }
                  
          }
  
          if( next === -1 ) R.clearOldID();
  
      }
docs: ---------------------- ID ----------------------