js leave or refresh page detection (and compatible with FF, IE, Chrome)_javascript skills

Copy code The code is as follows:

<script><br> function closeIt()<br> {<br> return "Any string value here forces a dialog box to n" <br> "appear before closing the window." ;<br> }<br> window.onbeforeunload = closeIt;<br></script>


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Compatible with FF, IE, and Chrome js detection for leaving or refreshing the page, the key part is to have return