Tryit Editor v1.8

Source Code:

<!DOCTYPE html>
<html>
<head>
<script>
function upperCase()
{
var x=document.getElementById("fname").value
document.getElementById("fname").value=x.toUpperCase()
}
</script>
</head>
<body>

<p>Enter your name, then move the cursor/tab outside the field:</p>
Enter your name: <input type="text" name="fname" id="fname" onblur="upperCase()">

</body>
</html>

Result:

W3Schools.com - Try it yourself

Edit the code above and click "Submit Code" to see the result.