Angular reactive forms pattern validator adding $ to regex and breaking validation

Question

I'm trying to validate a password with the following regex:
^(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.{8,}).
Note that there is no terminating $ char, because that would prevent valid passwords from being accepted. (I'm not sure why the input field doesn't terminate the string).
However, Angular's Validators.pattern adds the end of string char. And therefore my valid passwords fail.
How do I prevent the pattern validator from adding the $?
I suppose I could roll my own password validator, but surely there is a better solution...?

EDIT: Passwords that should succeed:

Test1234
tEst1234
tesT1234
1234Test
1234tesT
t#St1234

Passwords that should fail:

TEST1234
test1234
tEst123
Test123
testtest
12345678

Validator declaration:

this.password = new FormControl('', [Validators.required, Validators.pattern('^(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.{8,})')]);
this.userForm.addControl('Password', this.password);

Please give us one or two examples of what passwords you tried, and also how you declared your validator. — , Aug 08 '18 at 08:07

Wiktor Stribiżew · Accepted Answer · 2020-02-19T15:30:18.297

25

You may add a .* at the end, or even revamp the pattern a bit to convert one lookahead into a consuming pattern:

Validators.pattern('(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9]).{8,}')

Or, better, when using a regex for password validation, follow the principle of contrast:

Validators.pattern('(?=[^A-Z]*[A-Z])(?=[^a-z]*[a-z])(?=[^0-9]*[0-9]).{8,}')

Angular will add ^ and $ on both ends of the regex pattern, so the pattern will look like

^(?=[^A-Z]*[A-Z])(?=[^a-z]*[a-z])(?=[^0-9]*[0-9]).{8,}$

Note it won't add the anchors automatically if you use a regex literal, add them manually:

Validators.pattern(/^(?=[^A-Z]*[A-Z])(?=[^a-z]*[a-z])(?=\D*\d).{8,}$/)

With a regex literal, you may use single backslashes in regex escapes (/\d/ to match a digit vs. "\\d" in a string literal).

See the regex demo

Details

^ - start of string
(?=[^A-Z]*[A-Z]) - at least 1 uppercase ASCII letter
(?=[^a-z]*[a-z]) - at least 1 lowercase ASCII letter
(?=[^0-9]*[0-9]) - at least 1 ASCII digit
.{8,} - any 8 or more chars (other than line break chars)
$ - end of string.

edited Feb 19 '20 at 15:30

answered Aug 08 '18 at 08:08

Wiktor Stribiżew

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Changing the length lookahead to a consuming pattern solved it. Thanks. – AvailableName Aug 08 '18 at 08:20
Can i assign this dynamically i mean (?=[^A-Z]*[A-Z]) this code validates for 1 upper case letter what if i want 2 uppercase letters ? – Jignesh Mistry Dec 20 '18 at 08:20
1

@JigneshMistry Replace `(?=[^A-Z]*[A-Z])` with `(?=(?:[^A-Z]*[A-Z]){2})` – Wiktor Stribiżew Dec 20 '18 at 08:22
Thanks buddy it worked :) Just one more trouble can u send the regex for 2 Numeric & 2 special characters ? – Jignesh Mistry Dec 20 '18 at 08:29
@JigneshMistry They are formed the same way as above. – Wiktor Stribiżew Dec 20 '18 at 08:30
regex for special characters is not mentioned above – Jignesh Mistry Dec 20 '18 at 08:32
@JigneshMistry What chars do you consider special? Anyway, still, it will be formed the same way: `(?=(?:[^special_chars]*[special_chars]){2})` – Wiktor Stribiżew Dec 20 '18 at 08:34
! @ # $ % ^ & * ( ) - all these i am considering as special characters – Jignesh Mistry Dec 20 '18 at 08:35
@JigneshMistry So, I guess there is no problem with that. `(?=(?:[^!@#$%^&*()]*[!@#$%^&*()]){2})` – Wiktor Stribiżew Dec 20 '18 at 08:37
Angular is throwing this error after puting special characters ERROR SyntaxError: Invalid regular expression: /^(?=(?:[^!@#$%^&*()]*[!@#$%^&*()]){2})(?=(?:[^A-Z]*[A-Z]){1})(?:[^!-0]*[!-0]){2})(?=(?:[^0-9]*[0-9]){1}).{8,}$/: Unmatched ')' – Jignesh Mistry Dec 20 '18 at 08:39
@JigneshMistry Your pattern is corrupt. I think you wanted to write it as [`/^(?=(?:[^!@#$%^&*()]*[!@#$%^&*()]){2})(?=[^A-Z]*[A-Z])(?=(?:[^!-0]*[!-0]){2})(?=[^0-9]*[0-9]).{8,}$/`](https://regex101.com/r/S4ww0L/1) – Wiktor Stribiżew Dec 20 '18 at 08:42

Angular reactive forms pattern validator adding $ to regex and breaking validation

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