Javascript - innerHTML not working with HTML select menus

Question

In my HTML page I have 2 select menus with IDs "month" and "day" - "day" is empty when the page loads, "month" has 12 options with values 1-12 corresponding to January - December.

"month" has an onchange event which calls this function:

function showOutboundDays(month)
{
if(month==4 || month==6 || month==9 || month==11)
    document.getElementById('day').innerHTML='<option value="1">1</option><option value="2">2</option>'; etc. up to 30
else if(month==2)
    document.getElementById('day').innerHTML='<option value="1">1</option>'; etc. up to 28
else 
    document.getElementById('day').innerHTML='<option value="1">1</option>'; etc. up to 31
}

(just imagine there are braces around the option tags to help you see...)

I think it's pretty clear to see what I'm trying to achieve...and everything works fine apart from the innerHTML of the select with ID "day" doesn't get filled at all, regardless of what month you pick. And I know the problem is with this stage of the function because when I change the if, elseif and else code-to-be-executed to alerts or something similar, it works fine.

Does anybody know what the problem with the innerHTML is?

Thanks

EDIT: Using Firefox 3.6

Answer 1

I would suggest simply not to use innerHTML on a select - it just seems wrong. select elements have easy to use methods to add new options:

`document.getElementById('day').options.add(new Option("1", "1"))`

the parameters in the above object creation are:

new Option("optionText", "optionValue")

Just wanted to add to this answer, because it might clarify to someone who get to this post.