Regex email check not working correctly

Question

I have a problem with my regex. I didn't test this before. I have the following regex:

^(?:(?:[a-z])+(.|_)?(?!\.))*\w@(?:(?:[a-z])+(-|.)?(?!\.))*\w\.\w{2,}$

Now, my email validation halfly works. Here are some tests (according to regex101):

test -- invalid
test@ -- invalid
test@test -- invalid
test@test. -- invalid
[email protected] -- valid
[email protected]. -- invalid
test@[email protected] -- valid
[email protected] -- invalid

So, more than one @ can be used which is invalid for an email.

I kind of cannot see what I'm doing wrong.

NOTE:

I know there's a stackoverflow question that has a method on how to validate email with regex, HOWEVER: I'd like to know what I did wrong so I can learn from it.

@AndyKorneyev I'd rather know what I did wrong so I can learn from it. — Joshua Bakker
– Joshua Bakker, Commented Mar 30, 2017 at 8:54

Joshua Bakker · Accepted Answer · 2017-03-30 09:10:28Z

1

I found out the problem myself. The following regex does work:

^(?:(?:\w)+(\.|_)?(?!\.))*\w@(?:(?:[a-z])+(-|\.)?(?!\.))*[a-z]\.[a-z]{2,}$

I changed (.|_) into (\.|_) and (-|.) into (-|\.) to use . literally as a period and not as an 'all character "wildcard"'. I changed \w\.\w{2,} in [a-z]\.[a-z]{2,} to disallow _ in the last part.

answered Mar 30, 2017 at 9:10

Joshua Bakker

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2 Comments

Wiktor Stribiżew Over a year ago

(\.|_) is better replaced with [._]. And no need escaping the dot then.

Joshua Bakker Over a year ago

@WiktorStribiżew Thanks for the tip.

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