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The unload event is fired when the document or a child resource is being unloaded.

It is fired after:

  1. beforeunload (cancellable event)
  2. pagehide

The document is in a particular state:

  • All the resources still exist (img, iframe etc.)
  • Nothing is visible anymore to the end user
  • UI interactions are ineffective (window.open, alert, confirm, etc.)
  • An error won't stop the unloading workflow

Please note that the unload event also follows the document tree: parent frame unload will happen before child frame unload (see example below).

Bubbles No
Cancellable No
Target objects defaultView, Document, Element
Interface UIEvent if generated from a user interface, Event
Default action None

Properties

Property Type Description
target Read only EventTarget The event target (the topmost target in the DOM tree).
type Read only DOMString The type of event.
bubbles Read only Boolean Whether the event normally bubbles or not
cancelable Read only Boolean Whether the event is cancellable or not?
view Read only WindowProxy document.defaultView (window of the document)
detail Read only long (float) 0.

Example

<!DOCTYPE html>
<html>
  <head>
    <title>Parent Frame</title>
    <script>
      window.addEventListener('beforeunload', function(event) {
        console.log('I am the 1st one.');
      });
      window.addEventListener('unload', function(event) {
        console.log('I am the 3rd one.');
      });
    </script>
  </head>
  <body>
    <iframe src="child-frame.html"></iframe>
  </body>
</html>

Below, the content of child-frame.html:

<!DOCTYPE html>
<html>
  <head>
    <title>Child Frame</title>
    <script>
      window.addEventListener('beforeunload', function(event) {
        console.log('I am the 2nd one.');
      });
      window.addEventListener('unload', function(event) {
        console.log('I am the 4th and last one…');
      });
    </script>
  </head>
  <body>
      ☻
  </body>
</html>

When the parent frame is unloaded, events will be fired in the order described by console.log messages.

Specifications

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 最終更新者: bunnybooboo,