Regex non-consecutive chars

Question

Currently I have:

[A-Za-z0-9._%+-]

This matches any string that contains letters, numbers, and certain special chars (._%+-)

How can I change this so that it won't match a string that contains the special chars consecutively?

For example, I want it to match: foo.bar+test and foo.+bar and +foo.

But not: foo..bar+test or foo.bar++test or foo.bar++

Answer 1

If your tool/language supports look aheads, try:

^(?!.*([._%+-])\1)[A-Za-z0-9._%+-]+$