Question

I’m learning JavaScript and heard that document.getElementbyId() is quite useful.

So, I thought that I might make a form-checker that checks if the form field is blank.

Here is the jsFiddle (for some reason it isn’t displaying it correctly, you might want to make it a local file).

For some reason the alert() calls are not showing.

Answer 1

You are only testing if the textbox object is null. Not if the value in the HTMLInputElement is empty.

What you need is:

var LastName = document.getElementById('LastName');
if (LastName.value === '') {
    alert('Please enter a Last Name');
}