Javascript - Regex for allowing only selected special characters only

Question

I want to allow only specific special characters like in a text like ?*=.@#$%!^":,:;<'>+-_.

I have tried the below code:

pattern = new RegExp(/^(?=.*?[?*=.@#$%!^":,:;<'>+-_])/);

It does not seem to work, it seems to pass even if I am entering a special character other than the ones specified above. Am I missing something here?

e.g.:

var sampleText: string = "TestSample&123"

The above example should throw an error and fail since I have not used any of the special character which is specified in the pattern.

Can you provide an example? A quick test in the console and it seemed to work in the way I think you intend for it to... — Alexander Nied, Dec 09 '22 at 02:14
@LeandroBardelli : Because i am using a custom validator in a mat-password-strength which needs a regex pattern. — sTg, Dec 09 '22 at 02:20
Does this answer your question? [Matching special characters and letters in regex](https://stackoverflow.com/questions/13946651/matching-special-characters-and-letters-in-regex) — Leandro Bardelli, Dec 09 '22 at 02:27
@LeandroBardelli : no because i need only special characters and that too selected ones — sTg, Dec 09 '22 at 02:30

score 1 · Accepted Answer · answered Dec 09 '22 at 02:30

Based on the charset you want and the approach from this answer here about exclusive sets in Regex, you should be able to do something like this:

const testPattern = /^[?*=.@#$%!^":,;<'>+\-_]+$/;

console.log(testPattern.test('?*+@!')); // passes
console.log(testPattern.test('TestSample&123')); // fails

score 1 · Answer 2 · answered Dec 09 '22 at 02:33

A few things:

Javascript has regex literals, so you can do var regex = /^(?=.*?[?*=.@#$%!^":,:;<'>+-_])/ instead of new Regex(...)
https://regex101.com/ is a super helpful resource for figuring out regex. Paste ^(?=.*?[?*=.@#$%!^":,:;<'>+-_]) into that site and it'll explain what each part does.
The ^ at the beginning of the regex anchors the matching to the beginning of the string, but you don't have a corresponding $ to make sure the match applies to the entire string.
The (?=.*? is a positive lookahead that mathces any number of any character. The character group [...] that you have is only going to match a single character, when it sounds like you want it to match all of the characters.

Rahul already answered while I was typing this up, and he's got the right expression:

^[?*=.@#$%!^":,:;<'>+-_]*$

The ^ anchors the match to the beginning of the string, and the $ anchors the end of the match to the end of the string. The [...]* will match any number of characters as long as they belong to that set of characters.

You can make a JS var out this like

var myRegex = /^[?*=.@#$%!^":,:;<'>+-_]*$/

Rahul Tripathi · Answer 3 · 2022-12-09T02:34:13.483

0

You can try to use the below regex:

    const str = /^[a-zA-Z0-9?*=.@#$%!^":,:;<'>+-_]+$/;
    
    console.log(str.test('TestSample&123'));

edited Dec 09 '22 at 02:34

answered Dec 09 '22 at 02:26

Rahul Tripathi

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pattern = new RegExp(^[a-zA-Z0-9?*=.@#$%!^":,:;<'>+-_]+$); like this ???.. This gives me compile time error The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type – sTg Dec 09 '22 at 02:29

Javascript - Regex for allowing only selected special characters only

3 Answers3