HTML Conditional href - html

Question

I have a folder containing a large number of pdf files. They are named with a code of 3 digits (XXX.pdf). In that same folder, I have a index.html file, which as its name suggests, is an index for navigating in the folder and opening a specific pdf.
As an example, when I search a specific pdf file but I don't know what's the name of the pdf. I only know its title or authors.
Without that index, I have no solution to find it.
With the index, the pdf are classified according to authors or titles so I can search within the index and click on the link to open the file. The index contain this line for each pdf file:
<STRONG>TITLE001</STRONG><br /> Author001
So, this is the first configuration. I can give the entire folder to a colleague and he can open the index to search for a file as soon as he doesn't change the folder organization because the href link is relative.
Now, I have a second configuration in which I uploaded that folder on a server on a private network. I changed the index.html with the following line:
<STRONG>TITLE001</STRONG><br />Author001
In that way if someone search a specific pdf file, he can download the index and when he click on the like in that index, it will download the correct pdf from the server.
BUT, I would like to have both configuration working:
If my colleague uses a lot that folder, he will maybe prefer to download the entire folder and the index will not work because its not a relative address anymore.
If my colleague uses it occasionally, he will just download the index and it will work.
Is there any solution to merge both solution and to have a conditional href attribute ?
Allowing to use both configurations. Something like:
if "001.pdf" doesn't exist
<STRONG>TITLE001</STRONG><br />Author001
else
<STRONG>TITLE001</STRONG><br />Author001
Can someone help me with that ?
Thanks a lot !

Answer 1

Doubt you will find a way to do that in HTML, how about something with Js ? Do you use JQuery or something ?
Something like that could do it then :
$.ajax({
type: 'HEAD',
url: 'http://personal_cloud/001.pdf',
success: function() {
// here when then file does exist
},
error: function() {
// here when then file does not exist
}
});