Question

I got the regexp right. Works perfectly for Firefox ONLY. How would i make this cross browser, cross platform manner. Since it is file name and extension validation you are right i am using File Upload control.

^[a-zA-Z0-9_\.]{3,28}(.pdf|.txt|.doc|.docx|.png|.gif|.jpeg|.jpg|.zip|.rar)$

matches File name must not be empty[ 3, 28 characters long].

Extension must be within the group.

When this works superb in forefox i assume because the fileUpload.value = Filename.extension in firefox. It awfully fails in Google chrome and IE. I am using the above with .net Regular Expression validator and ClientScript enabled.

I know how to validate it on server, so please no server side solutions.

note:

Google chrome:

Provides the fileupload control value as c:\fakePath\filename.extension

IE:

Provides the Full path.

Answer 1

You can’t use the ^ to start with if you sometimes have a full path but are only interested in the filename. The dot of the filending should be escaped.

You could try something like this:

[^\\/]{3,}\.(pdf|txt|doc|docx|png|gif|jpeg|jpg|zip|rar)$

As it looks you get only the file with Firefox but the full path with other browsers.
I’d always add a prefix / to your string and than validate the last part after the last fileseprator / or \.

This example uses lookahead to check the fileseparator (or manually added /) before the file and also allows the check of max 28 char for filename. see this online regex tester:

(?<=[\\/])[\w\.]{3,28}\.(?:pdf|txt|doc|docx|png|gif|jpeg|jpg|zip|rar)$