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<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <title> JavaScript Event Listner </title> 
</head> 
<body>
  <button id="myBtn">Click Me</button>
 
 <script>
  // Defining custom functions
 function firstFunction() {
  alert("The first function executed successfully!");
  }
     
 function secondFunction() {
  alert("The second function executed successfully");
  }
     
  // Selecting button element
  var btn = document.getElementById("myBtn");
     
  // Assigning event handlers to the button
  btn.onclick = firstFunction;
  btn.onclick = secondFunction; // This one overwrite the first
</script>
</body>
</html>