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<!DOCTYPE html> <html> <body> <p>此示例使用 addEventListener() 方法将“beforeunload”事件附加到窗口对象。</p> <p>关闭此窗口，按 F5 或单击下面的链接以调用 beforeunload 事件。</p> <a href="https://www.begtut.com">点此进入begtut.com</a> <script> window.addEventListener("beforeunload", function(event) { event.returnValue = "在这里写点东西.."; }); </script> </body> </html>