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<!DOCTYPE html> <html> <body> <p>This example uses the addEventListener() method to attach a "beforeunload" event to the window object.</p> <p>Close this window, press F5 or click on the link below to invoke the beforeunload event.</p> <a href="../index.html">Click here to go to w3schools.com</a> <script> window.addEventListener("beforeunload", function(event) { event.returnValue = "Write something clever here.."; }); </script> </body> <!-- Mirrored from www.w3schools.com/jsref/tryit.asp?filename=tryjsref_onbeforeunload_addeventlistener by HTTrack Website Copier/3.x [XR&CO'2014], Fri, 23 Jan 2015 08:29:32 GMT --> </html>
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