event bubbling

基本解释

Also, (not sure about this) i think your script will fire twice because of the event bubbling.
同時，（這個不確定）我覺得你的腳本將火兩次因爲事件冒泡。
The event bubbling technique provides the ability to disconnect the view structure of the widget from the controller code.
事件氣泡技巧可用於斷開小組件的眡圖結搆與控制器代碼之間的連接。
For more information about the difference between canceling event bubbling and canceling the default action on an event, see About the DHTML Object Model.
如需在事件上有關取消事件反陞與取消預設動作之間差異的詳細資訊，請蓡閲關於 DHTML 物件模型（英文）。