Regular expression for folders

Question

I want a regular expression to test a string that meets the following requirements:

• It may contain a-z A-Z and 0-9
• It may contain - and _ but may not start nor end with these characters
• It may also contain a space but may not start nor end with it

It should match the following strings:

• folder_with some-content
• folderwithcontent
• folder_with_content
• folder-with content

Could someone please help me with it? Thanks in advance!

Answer 1

You have your pieces, so put them together:

/^[a-z0-9](?:[a-z0-9_ -]*[a-z0-9])?$/i

This does exactly what you're looking for. The only complicated part is allowing a single character.