VirtualMV/JavaScript/HelpDesk - Interactive

Overview
This page can be used in a group situation to discuss problems that can occur when coding. The problem is presented and after discussion a potential solution can be revealed.

Instructions
On this page you can post some JavaScript code that you are having trouble with.
 * Please keep the code "simple" concentrating on the problem ... not a lot of code with a "small" problem.
 * Post a tweet including the #vmvwiki tag so that we know there is a problem waiting to be solved.
 * Paste the following wiki code when you edit, and put your code where shown.

Problem 14: Checking a number has been entered
This is actually quite tricky but here is a solution

Problem 13: getElementById and innerHTML returns an error
You have entered the following code

and it returns

Error message: File.html:13 Uncaught TypeError: document.getElementByID is not a function

Problem 12: Opening a window and creating the hml file in js gives a blank window
In your JavaScript you have

Problem 11: changing code has noeffect
In your JavaScript you have

and even changing the code has no effect.

Problem 10: an input field won't accept background style
In the HTML you have entered the following code

In your JavaScript you have

and it returns and undefined error.

Problem 9: Trying to change the innerHTML of an element returns an error
You have entered the following code

and it returns and undefined error.

Problem 8: When you click Add row to a table, the row is added, the screen flashes and the row disappears
You have entered the following code

and When you click Add row to Table, the row is added, the screen flashes and the row disappears.

Problem 7: A getElementbyID doesn't work
You have entered the following code

and it doesn't work.

Problem 6: A window open causes a JavaScript error
You have entered the following code

and it doesn't work.

Problem 5: Adding two numbers js file
one.html

When Calculate button clicked - Error: Line 8, Character 5, Object expected

Problem 4: Linked js file
one.html

one.js