Dynamic password validator in angular 8

Question

Hi I have an api that returns an array object passwordPolicy that contains

PasswordMinLength: 6
passwordMinLowerCase: 1
passwordMinNumber: 1
passwordMinSymbol: 0
passwordMinUpperCase: 1

where the number can keep changing depending upon the role of a user example it can be

PasswordMinLength: Password min length.
PasswordMinLowerCase: This is currently either 0 or 1  So, if it's returning 1 for example it should have 1 minimum lower case. If it's returning 0 then the check should be ignored for lower case.
PasswordMinUpperCase: Same as above for upper case requirement.
PasswordMinSymbol: Same as above for symbol.
PasswordMinNumber: same as above to determine if a number is required in the password.

I know we can do validation using the regex pattern validation seeing the below How to validate password strength with Angular 5 Validator Pattern

but how to achieve validation DYNAMICALLY when the data keeps changing.

I need to validate the newpwdctrlname.

resetPwdForm: FormGroup = new FormGroup({
  newpwdctrlname: new FormControl('', [Validators.required, Validators.minLength(6)]),
  shownewpwdctrlname: new FormControl('', []),
  rptpwdctrlname: new FormControl('', [Validators.required])
});

Answer 1

You can generate the pattern dynamically using string interpolation

Something like

  passRequirement = {
    passwordMinLowerCase: 1,
    passwordMinNumber: 1,
    passwordMinSymbol: 2,
    passwordMinUpperCase: 1,
    passwordMinCharacters: 8
  };
  pattern = [
    `(?=([^a-z]*[a-z])\{${this.passRequirement.passwordMinLowerCase},\})`,
    `(?=([^A-Z]*[A-Z])\{${this.passRequirement.passwordMinUpperCase},\})`,
    `(?=([^0-9]*[0-9])\{${this.passRequirement.passwordMinNumber},\})`,
    `(?=(\.\*[\$\@\$\!\%\*\?\&])\{${this.passRequirement.passwordMinSymbol},\})`,
    `[A-Za-z\\d\$\@\$\!\%\*\?\&\.]{${
      this.passRequirement.passwordMinCharacters
    },}`
  ]
    .map(item => item.toString())
    .join("");
  resetPwdForm = this.fb.group({
    newpwdctrlname: ['Passwod1@@5', [Validators.required, Validators.pattern(this.pattern)]],
    shownewpwdctrlname: ['', []],
    rptpwdctrlname: ['', [Validators.required]]
  });
  constructor (private fb: FormBuilder) {}

You can then use this as

Validators.pattern(this.pattern)

See this demo on Stackblitz