I am working on email validations using regular expressions, where I need some fixed email values to validate before proceeding
Here is a clear requirement
User can only have up to 50 character before the Octets (#) and a maximum of 25 characters after the Octets, with a total of 80 characters
I used normal regex to validate email like
let reg = /^\w+([\.-]?\w+)*#\w+([\.-]?\w+)*(\.\w{2,3})+$/;
And now for the above requirement I am trying to create an expression like
let reg = /^\w+([\.-]?(\w{2,50})+)*#(\w{2,25})+([\.-]?\w+)*(\.\w{2,3})+$/;
But it's taking only starting character(not accepting lower than two) and not the last number of requirement, So any help would be appreciated.
If you want to match 1-50 word chars before the # (so no . or -) and 1-25 word chars after the # (also no . or -) and a total of no more than 80 chars:
^(?!.{81})(?:\w+[.-])*\w{1,50}#\w{1,25}(?:[.-]\w+)*\.\w{2,3}$
Explanation
^ Start of string
(?!.{81}) Negative lookahead, assert that from the current position there are not 81 chars directly to the right
(?:\w+[.-])* Repeat 0+ times 1+ word chars and either a . or -
\w{1,50} Match 1-50 word chars
# Match literally
\w{1,25} Match 1-25 word chars
(?:[.-]\w+)* Repeat 0+ times matching either a . or - and 1+ word chars
\.\w{2,3} Match a . and 2-3 word chars
$ End of string
Regex demo
Related
Need to create a regex for a string with below criteria
Allowable characters:
uppercase A to Z A-Z
lowercase a to z a-z
hyphen `
apostrophe '
single quote '
space
full stop .
numerals 0 to 9 0-9
Validations:
Must start with an alphabetic character a-zA-Z or apostrophe
Cannot have consecutive non-alpha characters except for a full stop followed by a space.
The regex I have from the previous question in this forum. Business came back and want to allow string starting with apostrophe along with [a-zA-Z]. This break some previous validations.
eg: a1rte is valid
'tyer4 is valid
'4rt is invalid
^(?!.*[0-9'`\.\s-]{2})[a-zA-Z][a-zA-Z0-9-`'.\s]+$
Please advise.
You might use
^(?=[a-zA-Z0-9`'. -]+$)(?!.*[0-9'` -]{2})[a-zA-Z'][^\r\n.]*(?:\.[ a-z][^\r\n.]*)*$
Explanation
^ Start of string
(?=[a-zA-Z0-9`'. -]+$) Assert only allowed characters
(?!.*[0-9'` -]{2}) Assert not 2 consecutive listed characters
[a-zA-Z'] Match either a char a-zA-Z or apostrophe
[^\r\n.]* Optionally match any char except a newline or a dot
(?:\.[ a-z][^\r\n.]*)* Optionally repeat matching a dot only followed by a space or char a-z
$ End of string
Regex demo
Use lookaheads to match a string that is greater than 5 characters long and have two consecutive digits.
I know the solution should be
/(?=\w{6,})(?=\D*\d{2})/
But why the second element is
(?=\D*\d{2})
Instead of
(?=\d{2})
Please help me to understand this.
Actually, /(?=\w{6,})(?=\D*\d{2})/ does not ensure there will be a match in a string with 2 consecutive digits.
Check this demo:
var reg = /(?=\w{6,})(?=\D*\d{2})/;
console.log(reg.test("Matches are found 12."))
console.log(reg.test("Matches are not found 1 here 12."))
This happens because \D* only matches any non-digit chars, and once the \w{6,} matches, (?=\D*\d{2}) wants to find the two digits after any 0+ digits, but it is not the case in the string.
So, (?=\w{6,})(?=\D*\d{2}) matches a location in the string that is immediately followed with 6 or more word chars and any 0+ non-digit chars followed with 2 digits.
The correct regex to validate if a string contains 6 or more word chars and two consecutive digits anywhere in the string is
var reg = /^(?=.*\w{6,})(?=.*\d{2})/;
Or, to support multiline strings:
var reg = /^(?=[^]*\w{6,})(?=[^]*\d{2})/;
where [^] matches any char. Also, [^] can be replaced with [\s\S] / [\d\D] or [\w\W].
And to match a string that is greater than 5 characters long and have two consecutive digits you may use
var reg = /^(?=.*\d{2}).{5,}$/
var reg = /^(?=[\s\S]*\d{2})[\s\S]{5,}$/
where
^ - start of string
(?=[\s\S]*\d{2}) - there must be two digits anywhere after 0+ chars to the right of the current location
[\s\S]{5,} - five or more chars
$ - end of string.
The lookahead has to allow the 2 digits anywhere in the input. If you used just (?=\d{2}) then the 2 digits would have to be at the beginning.
You could also use (?=.*\d{2}). The point is that \d{2} has to be preceded by something that can match the rest of the input before the digits.
I'm trying to validate a string entered by the user to be used as the statement description on the credit card statement to describe the purchase.
The requirements are:
Must be between 5 and 22 characters long
Must contain at least one letter (case doesn't matter)
Cannot contain these characters: < > \ ' "
Only ASCII characters allowed
Here's what I've got so far, which is kind of working:
/^(?=.*?[a-zA-Z])[a-zA-Z0-9]{5,22}$/gm
...in that it correctly checks the length for 5-22 characters long and checks for at least one letter. However, it disallows all special characters and diacritics instead of just the few that aren't allowed. How do I modify it to allow the other allowed characters?
You could use a positive lookahead to assert a character and a negative lookahead to assert not to match any character listed in the character class.
For Javascript you can use the case insensitive flag /i and use [a-z].
Edit: As Wiktor Stribiżew points out, to match only ASCII characters you could use [\x00-\x7F] instead of using a dot.
^(?=.*[a-z])(?!.*[<>\\'"])[\x00-\x7F]{5,22}$
^ Start of string
(?=.*[a-z]) Positive lookahead to check if there is a ASCII letter
(?!.*[<>\\'"]) Negative lookahead to check that there is not any of the chars in the character class
[\x00-\x7F]{5,22} Match any ASCII character 5 - 22 times
$ End of the string
For example:
const regex = /^(?=.*[a-z])(?!.*[<>\\'"])[\x00-\x7F]{5,22}$/gmi;
See the regex demo
You may use
/^(?=[^a-z]*[a-z])(?:(?![<>\\'"])[\x00-\x7F]){5,22}$/i
/^(?=[^a-z]*[a-z])(?![^<>\\'"]*[<>\\'"])[\x00-\x7F]{5,22}$/i
If you mean printable ASCII chars are allowed use
/^(?=[^a-z]*[a-z])(?:(?![<>\\'"])[ -~]){5,22}$/i
/^(?=[^a-z]*[a-z])(?![^<>\\'"]*[<>\\'"])[ -~]{5,22}$/i
Details
^ - start of string
(?=[^a-z]*[a-z]) - there must be at least 1 ASCII letter in the string
(?:(?![<>\\'"])[ -~]){5,22} - five to twenty-two occurrences of any printable ASCII char other than <, >, \, ' and " (if [\x00-\x7F] is used, any ASCII char other than the chars in the negated character class)
(?![^<>\\'"]*[<>\\'"]) - no <, >, \, ' and " allowed in the string
$ - end of string.
Hi all I am making a password regular expression in javascript test() method, It will take the following inputs
solution
/^(?=.*\d)^(?=.*[!#$%'*+\-/=?^_{}|~])(?=.*[A-Z])(?=.*[a-z])\S{8,15}$/gm
May contains any letter except space
At least 8 characters long but not more the 15 character
Take at least one uppercase and one lowercase letter
Take at least one numeric and one special character
But I am not able to perform below task with (period, dot, fullStop)
(dot, period, full stop) provided that it is not the first or last character, and provided also that it does not appear two or more times consecutively.
Can anyone one help me to sort out this problem, Thanks in advance
You may move the \S{8,15} part with the $ anchor to the positive lookahead and place it as the first condition (to fail the whole string if it has spaces, or the length is less than 8 or more than 15) and replace that pattern with [^.]+(?:\.[^.]+)* consuming subpattern.
/^(?=\S{8,15}$)(?=.*\d)(?=.*[!#$%'*+\/=?^_{}|~-])(?=.*[A-Z])(?=.*[a-z])[^.]+(?:\.[^.]+)*$/
See the regex demo
Details:
^ - start of string
(?=\S{8,15}$) - the first condition that requires the string to have no whitespaces and be of 8 to 15 chars in length
(?=.*\d) - there must be a digit after any 0+ chars
(?=.*[!#$%'*+\/=?^_{}|~-]) - there must be one symbol from the defined set after any 0+ chars
(?=.*[A-Z]) - an uppercase ASCII letter is required
(?=.*[a-z]) - a lowercase ASCII letter is required
[^.]+(?:\.[^.]+)* - 1+ chars other than ., followed with 0 or more sequences of a . followed with 1 or more chars other than a dot (note that we do not have to add \s into these 2 negated character classes as the first lookahead already prevalidated the whole string, together with its length)
$ - end of string.
I want an existing email regex to fail when entering a period (".") before the #.
This is the regex I have right now:
^[a-zA-Z]+[a-zA-Z0-9.]+#domain.com$
These should pass:
test.a#domain.com
a.test#domain.com
But these shouldn't:
.test#domain.com
test.#domain.com
The first case starting with period is handled but second case is not.
This should work without requiring two or more characters before the # sign.
^[a-zA-Z][a-zA-Z0-9]*(?:\.+[a-zA-Z0-9]+)*#domain\.com$
Here's how it breaks down:
^ Make sure we start at the beginning of the string
[a-zA-Z] First character needs to be a letter
[a-zA-Z0-9]* ...possibly followed by any number of letters or numbers.
(?: Start a non-capturing group
\.+ Match any periods...
[a-zA-Z0-9]+ ...followed by at least one letter or number
)* The whole group can appear zero or more times, to
offset the + quantifiers inside. Otherwise the
period would be required
#domain\.com$ Match the rest of the string. At this point, the
only periods we've allowed are followed by at
least one number or letter
I would try:
^[a-zA-Z]+[a-zA-Z0-9.]*[a-zA-Z0-9]+#domain.com$
Try this regex: ^[\w.+-]*[^\W.]#domain\.com$.
[\w.+-]* matches any number of alphanumerical characters, +, - and .
[^\W.] matches any character that is not a non-alphanumerical character or a . (which means any accepted character but .)
#domain\.com matches the rest of the email, change the domain as you wish or use #\w\.\w+ for matching most domains. (matching all domains is more complex, see more complete examples of email matching regex here)