Remove invalid characters from email

Question

I want to help users from mistakenly entering invalid characters in an email input (pre server-side validation/cleanup)

Note: I am NOT validating emails in frontend, just cleaning up

// Coffeescript
$(Element).find('input[type="email"]').on 'change keyup', (event) ->
    I = $(this)
    V = I.val()
    I.val(V.replace( [what goes here?] , ''))

I want remove space and illegal characters.

What's my regex pattern?

What goes there is a regular expression that matches all the bad characters. An inverted character set is an easy way to do it. — Barmar, Nov 11 '14 at 00:58

james emanon · Answer 1 · 2014-11-11T02:10:37.683

5

Something like. I am saying, strip things that are NOT what I want. But to be honest, I do not know what are acceptable email chars.

.replace(/[^a-zA-Z0-9_-@.]/g,'')

edited Nov 11 '14 at 02:10

answered Nov 11 '14 at 01:03

james emanon

11,185
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4

You forgot to escape `-` symbol, working piece of code: `"test_email_validation||@example.com".replace(/[^a-zA-Z0-9_/-@.]/g,'');` – Ilya Khadykin Jan 14 '17 at 12:14

score 5 · Answer 2 · edited Oct 07 '21 at 06:01

If you truly want to "cleanup" an email. Then you need to refer to the RFCs relating to emails. You're in for a lot of trouble. You can do it in a Regex if you're so inclined, but it'll be a fairly complicated Regex unless you decide on a subset of valid email addresses.

Here's some relevant links to read about this

Here's a list of valid characters (from Wikipedia)

Uppercase and lowercase English letters (a–z, A–Z) (ASCII: 65–90, 97–122)

Digits 0 to 9 (ASCII: 48–57)

These special characters: ! # $ % & ' * + - / = ? ^ _ ` { | } ~

Character . (dot, period, full stop) (ASCII: 46) provided that it is not the first or last character, and provided also that it does not appear consecutively (e.g. John..Doe@example.com is not allowed).

Special characters are allowed with restrictions. They are:

Space and "(),:;<>@[] (ASCII: 32, 34, 40, 41, 44, 58, 59, 60, 62, 64, 91–93) The restrictions for special characters are that they must only be used when contained between quotation marks, and that 2 of them (the backslash \ and quotation mark " (ASCII: 92, 34)) must also be preceded by a backslash \ (e.g. "\"").[citation needed]

Comments are allowed with parentheses at either end of the local part; e.g. "john.smith(comment)@example.com" and "(comment)john.smith@example.com" are both equivalent to "john.smith@example.com".

International characters above U+007F, encoded as UTF-8, are permitted by RFC 6531, though mail systems may restrict which characters to use when assigning local parts.

The point I'm trying to make is be careful of limiting what a user can enter simply because you think it's invalid. For instance, a common thing I do is place a plus sign in my email. So I'd do something+website.com@domain.com. The reason for this is I know exactly what website I gave my email address too (also makes filtering easier). Along with a few other reasons, but it's annoying when a website can't support a valid email addresses. (happens more times than I care to mention)

Then once you've validated the email contains valid characters, there still is no guarantee that the email provided is a valid email.

Anyways if this is truly what you want to do. Here's a regex that supports the email according to the RFC.

Credit goes to this guy

(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ 
\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\0
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)
?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\
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 \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*
)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
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Remove invalid characters from email

2 Answers2

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