<!DOCTYPE html>
<html>
<body>
<p>Counting with a local variable.</p>
<button type="button" onclick="myFunction()">Count!</button>
<p id="demo">0</p>
<script>
var add = (function () {
var counter = 0;
return function () {return counter += 1;}
})();
function myFunction(){
document.getElementById("demo").innerHTML = add();
}
</script>
</body>
</html>