http://sinhviencntt.net/hoc-javascript-bai-12-cac-kieu-du-lieu-trong-javascript/

http://sinhviencntt.net/hoc-javascript-bai-12-cac-kieu-du-lieu-trong-javascript/

by sinhviencntt

HTML

<!DOCTYPE html>
<html>
<body>
 
<p>Undefined Trong JavaScript</p>
 
<p id="demo"></p>
 
<script>
var x;
document.getElementById("demo").innerHTML = x
</script>
 
</body>
</html>