<!DOCTYPE html>
<html>
<body>
<p>Click the button to display the extracted part of the string.</p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var str = "Hello world!";
var res = str.slice(0);
document.getElementById("demo").innerHTML = res;
}
</script>
</body>
</html>