<!DOCTYPE html>
<html>
<body>
<p>This example uses the HTML DOM to assign an "onblur" event to an input element.</p>
<p>Write something in the input field, and then click outside the field to lose focus (blur).</p>
<input type="text" id="fname">
<script>
document.getElementById("fname").onblur = function() {myFunction()};
function myFunction() {
alert("Input field lost focus.");
}
</script>
</body>
</html>