//Changing the case
// modern js
document.getElementById("result").innerHTML = 'Interface'.toUpperCase();
document.getElementById("result").innerHTML += '<br />';
document.getElementById("result").innerHTML += 'Interface'.toLowerCase();
document.getElementById("result").innerHTML += '<br />';
document.getElementById("result").innerHTML += 'Interface'[0].toLowerCase();
<h1>String</h1> <h2>Changing the case</h2> <blockquote> result:<br /> <span id="result"></span> </blockquote>