Javascript: How to remove illegal URL characters from a file name?

Question

How to remove illegal URL characters from a file name but not the dot on file extension? Is there a way to do this? Currently I have this

fileName = "I am a file name + two.doc"
fileName.replace(/[^a-zA-Z0-9-_]/g, ''); // regex that removes illegal characters

But it also removes the . on the .doc I want something that will remove illegal characters except the file extension. Is it possible?

Answer 1

Add the . literal as well then, \\. :

var fileName = "I am a file name + two.doc";
fileName.replace(/[^a-zA-Z0-9-_\.]/g, ''); // 'Iamafilenametwo.doc'

It's worth pointing out that the . character in a regular expression will match any single character except the newline character . Therefore you needed to escape the character in order for it to match the literal character, \\.

Also, \\w is equivilant to [A-Za-z0-9_] , therefore you could shorten your expression to:

/[^\w.]/g

And as hwnd points out , if you don't want to allow other dot characters inside the filename, you can use subtraction:

.replace(/(?!\.[^.]+$)\.|[^\w.]+/g, '')

Answer 2

For Windows filenames, I believe a simplified version of the .replace should be
.replace(/[\\\\/:"*?<>|]/g, '')