正则表达式匹配一堆字符+仅一个|

Question

I have a regex that works great for matching the following..

^[a-z-&+/]

Now I want add in a match for the "|" symbol, but only if it starts with a single "|"

True results

|hello
apple
test||test

False Results

||hello

I tried a bunch of ways on regex101.com - but I can't come up with the right regex.

Answer 1

This regex works for what you want:

^([a-z-&+\/]|\|(?!\|))

This goes from the start of the input, tries to find any of your original characters ( [az-&+/] ) OR a | not followed by a | (using a negative lookahead).

See a demo on regex101.com .

Answer 2

This worked for me:

                      /^[|a-z-&+/](?!\|)/

One can use | inside character set as well. Check http://www.regexr.com/3coad where i tested the match.