code: function(flag) {
  			flag = flag !== false; // Confusing use of '!'
  			/*jshint -W018 */ if (!!this._enableUpdate === !!flag) {
  				return flag;
  			}
  			/*jshint +W018 */
  			this._enableUpdate = flag;
  			if (flag) {
  				this.debug("enableUpdate(true): redraw "); //, this._dirtyRoots);
  				this.render();
  			} else {
  				// 	this._dirtyRoots = null;
  				this.debug("enableUpdate(false)...");
  			}
  			return !flag; // return previous value
  		}
docs: Temporarily suppress rendering to improve performance on bulk-updates.
  
  @param {boolean} flag
  @returns {boolean} previous status
  @since 2.19