javascript事件流机制

原文：

Event flow in DOM Level 2

Consider the situation when there are 2 elements nested together. Both have event handlers registered on the same event type, say "click". When the user clicks on the inner element, there are two possible ways to handle it:

• Trigger the elements from outer to inner (event capturing). This model is implemented in Netscape Navigator .
• Trigger the elements from inner to outer (event bubbling). This model is implemented in Internet Explorer and other browsers.

W3C takes a middle position in this struggle. Events are first captured until it reaches the target element, and then bubbled up. During the event flow, an event can be responded to at any element in the path (an observer) in either phase by causing an action, and/or by stopping the event (with method event.stopPropagation() for Mozilla and command event.cancelBubble = true for Internet Explorer), and/or by cancelling the default action for the event.