I am trying to create a regex for specific format of email addresses:
Before the @ sign:
- Allow only English letters and numbers.
- Allow dots, dashes and underscores as long as they are not consecutive, and don't allow them to be the last in the string (They have to followed by a letter or a number)
After the @ sign:
- Allow only single dot
- TLD has to be minimum 2 letters (currently I also set to 24 maximum but that doesn't matter)
I also allow spaces before and after the entire string (And later trim them)
I managed to get to a working regex that almost matches everything above, except for the part where the special characters (dots, dashes and underscores) have to be followed by a letter or a number.
so this is the regex that works:
/^\s*(?!.*[._-]{2})[\w\.-] @([\w-]) \. [\w-]{2,24}\s*$/
Then I tried adding the part that matches with a letter or a number after the special char but it breaks everything:
(?=[A-Z\d])
So it looks: /^\s*(?!.*[._-]{2})[\w\.-] (?=[A-Z\d]) @([\w-]) \. [\w-]{2,24}\s*$/
But that doesn't work
Test data:
### Should match:
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
### Should not match but still matches:
[email protected]
## Should not match and doesn't match (so working correctly):
[email protected]
email@,domain.com
demo: https://regex101.com/r/qYMQlt/1
CodePudding user response：
You could use a negated character class [^\W_] to match word characters without the _
To not match 2 special characters in a row you don't have to use a negative lookahead (?!.*[._-]{2}), but you can repeat matching using a group and start with the "special" character followed by at least 1 or more times other characters.
^Start of string\s*Match optional whitespace chars[^\W_]Match 1 times a word char without the underscore(?:[._-][^\W_] )*Optionally repeat the same, but allow a single char._-@Match literally[^\W_]Match 1 times a word char without the underscore(?:[_-][^\W_] )*Optionally repeat the same, but allow a single char._-\.[\w-]{2,24}Match.and repeat matching 2-24 times either a word char or-(Note that this can also match 24 times a hyphen, perhaps use[a-z]{2,})\s*Match optional whitespace chars$End of string