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If I attach multiple event handlers to a single event on a single DOM element, are the event handlers guaranteed to be called in the order they were added? Or should I not rely on this behavior?
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1) Currently they are executed in the order that the implementation of the specific event dictates - since you can implement your own add/remove methods for events. 2) When using the default event implementation via multi-cast delegates, the order is in fact required by specifications.
JavaScript Event HandlersEvent handlers can be used to handle and verify user input, user actions, and browser actions: Things that should be done every time a page loads. Things that should be done when the page is closed. Action that should be performed when a user clicks a button.
Event capturing the event handler of element1 fires first, the event handler of element2 fires last.
This has been changed with DOM3! While the DOM level 2 events specification did state
When the event reaches the target, any event listeners registered on the
EventTargetare triggered. Although allEventListenerson theEventTargetare guaranteed to be triggered by any event which is received by thatEventTarget, no specification is made as to the order in which they will receive the event with regards to the otherEventListenerson theEventTarget.
The current DOM level 3 events specification does now state
The implementation MUST determine the current target's candidate event listeners. This MUST be the list of all event listeners that have been registered on the current target in their order of registration.
HTML5defines the ordering of listeners registered through event handler attributes. […]Finally, the implementation MUST process all candidate event handlers in order […]
However, I can't find a reference to this behaviour in the DOM 4 draft any more.
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