The onkeyup event triggers when a key is released.
Example
You can try to run the following code to learn how to work with onkeyup event in JavaScript −
<html>
<head>
<script>
<!--
function sayHello() {
var str = document.getElementById("subject");
str.value = str.value.toLowerCase();
}
//-->
</script>
</head>
<body>
<p>Enter subject below in upper case and see what happpens.</p>
<input type = "text" onkeyup = "sayHello()" id = "subject">
</body>
</html>