coderatchet/goog-events-eventtype-beforeunload-tabclose.html

## goog-events-eventtype-beforeunload-tabclose.html
<!doctype html>
<html lang="en">
<head>
    <title>BEFOREUNLOAD intercept example</title>
</head>
<body>
<h1>Try to close me!</h1>
<form action="javascript:console.log('stop poking me!');">
    <label for="something">sometimes you need to interact with the page before the browser will prompt you.</label><input type="text" id="something" />
    <input type="submit" />
</form>
<!--Ensure that the closure-library folder lies in the same directory as this file. -->
<script src="./closure-library/closure/goog/base.js"></script>
<script type="application/javascript" language="JavaScript">
    goog.require('goog.dom');
    goog.require('goog.events.EventType');
    </script>
<script type="application/javascript" language="JavaScript">
    console.log('I executed');
    var handlerFn = function (event) {
        var message = "are you sure you want to leave?";
        event.returnValue = message; // this message won't show in most modern browsers. something like "you are
        // about to leave, you may lose any unsaved data on this page." will show instead.
        return message;
    };
    window.addEventListener(goog.events.EventType.BEFOREUNLOAD, handlerFn);
</script>
</body>
</html>
	<!doctype html>
	<html lang="en">
	<head>
	<title>BEFOREUNLOAD intercept example</title>
	</head>
	<body>
	<h1>Try to close me!</h1>
	<form action="javascript:console.log('stop poking me!');">
	<label for="something">sometimes you need to interact with the page before the browser will prompt you.</label><input type="text" id="something" />
	<input type="submit" />
	</form>
	<!--Ensure that the closure-library folder lies in the same directory as this file. -->
	<script src="./closure-library/closure/goog/base.js"></script>
	<script type="application/javascript" language="JavaScript">
	goog.require('goog.dom');
	goog.require('goog.events.EventType');
	</script>
	<script type="application/javascript" language="JavaScript">
	console.log('I executed');
	var handlerFn = function (event) {
	var message = "are you sure you want to leave?";
	event.returnValue = message; // this message won't show in most modern browsers. something like "you are
	// about to leave, you may lose any unsaved data on this page." will show instead.
	return message;
	};
	window.addEventListener(goog.events.EventType.BEFOREUNLOAD, handlerFn);
	</script>
	</body>
	</html>