The description of the OnUnload event in the HTML 4.01 specification is that the OnUnload event is triggered when document is removed from the window.
About the OnUnload intrinsic event description in the HTML 4.01 specification: Http://www.w3.org/TR/html401/interact/scripts.html#adef-onunload.
Description of the OnUnload event in MSDN: http://msdn.microsoft.com/en-us/library/ms536973 (vs.85). aspx.
Description of the OnUnload event in Mozilla Developer Center: https://developer.mozilla.org/en/DOM/window.onunload.
Problem descriptionWhen document is removed from the window, the OnUnload event is triggered, and the browser support for the OnUnload event differs from the trigger condition implementation.
The impactEach browser's support for OnUnload events differs from the trigger condition implementation, so the methods written in the OnUnload event may not be executed in some browsers.
The affected browser| All browsers |
|---|
As described in MSDN, the OnUnload event for IE can be triggered by the following conditions:
Most of these trigger conditions start with a jump in the page, but there is a lack of a common scenario where the page URL may have changed but no jumps have occurred. For example, "Javascipt:" "mailto:" and other common browser built-in pseudo-protocol, as well as by a third party or user-defined as a protocol, the page does not jump, but according to the pseudo-protocol to perform the specified behavior. This condition should be added to the trigger condition.
Based on all of these trigger conditions, we construct the following code to detect the level of support and trigger conditions for each browser for the OnUnload event:
<! DOCTYPE Html>Summary of execution results into the table:
| IE6 | IE7 | IE8 | Firefox | Chrome | Safari | Opera | |
|---|---|---|---|---|---|---|---|
| Close the current browser window | Event is triggered | Event not triggered | Event not triggered | Event is triggered | Event is triggered | Event not triggered | Event not triggered |
| Navigate to another to enter a new address or choose a favorite location | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event not triggered |
| Click Back, Forward, refresh, or home button | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event not triggered |
| Click on a link to a new page | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered |
| Calling the Anchor.click method | Event is triggered | Event is triggered | Event is triggered | This method is not supported 1 | This method is not supported 1 | This method is not supported 1 | Event is triggered |
| Calling the Document.Write method | Event is triggered | Event is triggered | Event is triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered |
| Calling the Document.open method | Event is triggered | Event is triggered | Event is triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered |
| Calling the Document.close method | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered |
| Call the Window.Open method, and the window name setting value is _self | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered |
| Call Window.navigate | Event is triggered | Event is triggered | Event is triggered | This method is not supported 2 | This method is not supported 2 | This method is not supported 2 | Event not triggered |
| Calling the Navigateandfind method | Event is triggered | Event is triggered | Event is triggered | This method is not supported 3 | This method is not supported 3 | This method is not supported 3 | This method is not supported 3 |
| Calling the Location.replace method | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event not triggered |
| Calling the Location.reload method | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event not triggered |
| Specify a new value for the Location.href property | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered |
| Submit a form using the Submit button | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered |
| Calling the Form.submit method | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered | Event is triggered |
| Call Javascipt: Pseudo-protocol | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered |
| Call mailto: pseudo-protocol | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered |
| Invoking a custom pseudo-protocol | Event is triggered | Event not triggered | Event not triggered | Event not triggered | Event not triggered | Event is triggered | Event not triggered |
"Note 1": The click Method of directly invoking the link element simulates mouse click events, only IE and Opera support.
"Note 2": Using the Window.navigate method to navigate the page is only supported by IE Opera, you can refer to the MSDN Original: Navigate method.
"Note 3": The Navigateandfind method is in the Window.External object, external object is also only IE support, you can refer to the MSDN Original: Navigateandfind method and the article Bt9012:ie E The Xternal object provides methods that are specific to IE.
In conjunction with the summary table, you can see:
There are many differences between browser support and event triggering conditions, so use caution.
Browser support for OnUnload events differs from trigger condition implementation
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