How to write Conditional regex? - reactjs

Question

I want to use Yup for validation. in a part of validation I have
const validationSchema = Yup.object({password: Yup.string().matches(passwordRegex, "passRegex")})
passWordRegex is a varibale that contains a regex :
const passwordRegex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[#$!%*?&])[A-Za-z\d#$!%*?&]{4,32}$/;
I have some booleans that determine that if for example small letter or big letter or speciall character is needed in password or not:
smallLetter = false
capitalLetter = true
specialChar = true
now my regex ( passwordRegex variable) is not conditional . how can I write a regex (passwordRegex variable) conditional base on my Boolean variables

Answer 1

You could build the regex string you want and then create a proper RegExp object:
var input = "aB#3";
var smallLetter = false;
var capitalLetter = true;
var specialChar = true;
var number = true;
var regex = "";
if (smallLetter) regex += "(?=.*[a-z])";
if (capitalLetter) regex += "(?=.*[A-Z])";
if (specialChar) regex += "(?=.*[#$!%*?&])";
if (number) regex += "(?=.*[0-9])";
regex = "^" + regex + "[A-Za-z0-9#$!%*?&]{4,32}$";
var re = new RegExp(regex);
if (re.test(input)) {
console.log(input + " => valid");
}