unload

å¯åæ³¡ï¼Bubblesï¼	No
å¯åæ¶ï¼Cancelableï¼	No
æ¥å£ï¼Interfaceï¼	`Event`
äºä»¶å¤çç¨åºå±æ§ï¼Event handler propertyï¼	`onunload`

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beforeunload (å¯åæ¶é»è®¤è¡ä¸ºçäºä»¶)
pagehide

ææ¡£å¤äºä»¥ä¸ç¶æï¼

ææèµæºä»åå¨ (å¾çï¼iframe ç.)
å¯¹äºç»ç«¯ç¨æ·ææèµæºåä¸å¯è§
çé¢äº¤äºæ æ (window.open, alert, confirm ç.)
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è¯·æ³¨æunloadäºä»¶ä¹éµå¾ªææ¡£æ ï¼ç¶ iframe ä¼å¨å iframe å¸è½½åå¸è½½ (åèä¸é¢çä¾å).

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html

<!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>

ä¸é¢æ¯ child-frame.html çåå®¹:

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 oneâ¦");
      });
    </script>
  </head>
  <body>
    â»
  </body>
</html>

å½ç¶ iframe è¢«å¸è½½ï¼äºä»¶å°æ console.log() æ¶æ¯æè¿°çé¡ºåºè§¦åã