Change onclick action with a Javascript function

Question

I have a button:

Button A

When I click this button the first time, I want it to exe

Answer 1

Your code is calling the function and assigning the return value to onClick, also it should be 'onclick'. This is how it should look.

document.getElementById("a").onclick = Bar;

Looking at your other code you probably want to do something like this:

document.getElementById(id+"Button").onclick = function() { HideError(id); }