Call a JavaScript Function From a String With window variable-cpming

<!DOCTYPE html>
<html>
<head>
<title>Call a JavaScript Function From a String With window variable</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script>
// Define a method
function testFunc(str) {
   return "Hello: " + str;
}
$(function (){
   $("#btn").click(function (){
   var params = $("#name").val();
   // Call the method
   var funcName = "testFunc";
   if (window[funcName] != null && typeof window[funcName] === "function") {
   var ret = window[funcName](params);
   // Output
   $("#result").text(ret);
   }
   });
});
</script>
</head>
<body>
<div>
   <input type="text" id="name" placeholder="Input a name" />
   <button id="btn">Start</button>
</div>
<div id="result"></div>
</body>
</html>