<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
<style>
#w3docs {
color: #666;
}
</style>
</head>
<body>
<h1 id="w3docs">Example</h1>
<button onclick="displayResult()">
Click here
</button>
<script>
function displayResult() {
document.getElementById(
"w3docs")
.innerHTML = "Hello world!";
}
</script>
</body>
</html>