The following code shows an Example of Onload and OnBeforeUnload in JavaScript. As can be seen the following ite a JavaScript code block, greets a user with a message Welcome’. When a user leaves this page, the alert dialog box is displayed.

<html>
 <head>
   <title>OnBeforeUnload Example</title>
   <script>
     function f1()
      {
          alert("Welcome to JavaScript Event Handling!");
      }
      function f2(){ return "bye...";}
   </script>
   <style>
     body{
       text-align: center;
       font-size: 30px;
       background: #ee6699;
       padding: 30px;
     }
   </style>
 </head>
 <body onload="f1();" onbeforeunload="return f2();">
    <h1>JavaScript OnLoad and OnBeforeUnload Event Handling!</h1>
    <a href="https://www.programmingempire.com" target="_blank">Programmingempire</a>
 </body>
</html>