password and confirm password field validation angular2 reactive forms

Question

I need to check whether password and confirm password fields have same value using reactive form angular2. I did see a lot of answers on the same here,Angular 2 form validating for repeat password ,Comparing fields in validator with angular2, but none seemed to work for me.Can someone please help."this" is undefined in my validate function :( . Sharing my code,

this.addEditUserForm = this.builder.group({
            firstName: ['', Validators.required],
            lastName: ['', Validators.required],
            title: ['', Validators.required],
            email: ['', Validators.required],
            password: ['', Validators.required],
            confirmPass: ['', [Validators.required, this.validatePasswordConfirmation]]
        });
validatePasswordConfirmation(group: FormGroup): any{
        let valid = true;
        // if (this.addEditUserForm.controls.password != this.addEditUserForm.controls.confirmPass) {
        //     valid = false;
        //     this.addEditUserForm.controls.confirmPass.setErrors({validatePasswordConfirmation: true});
        // }
        return valid;
    }

Answer 1

This is what eventually worked for me -

this.addEditUserForm = this.builder.group({
            firstName: ['', Validators.required],
            lastName: ['', Validators.required],
            title: ['', Validators.required],
            email: ['', Validators.required],
            password: ['', Validators.required],
            confirmPass: ['', Validators.required]
        },{validator: this.checkIfMatchingPasswords('password', 'confirmPass')});



checkIfMatchingPasswords(passwordKey: string, passwordConfirmationKey: string) {
          return (group: FormGroup) => {
            let passwordInput = group.controls[passwordKey],
                passwordConfirmationInput = group.controls[passwordConfirmationKey];
            if (passwordInput.value !== passwordConfirmationInput.value) {
              return passwordConfirmationInput.setErrors({notEquivalent: true})
            }
            else {
                return passwordConfirmationInput.setErrors(null);
            }
          }
        }

Answer 2

Best would be to have a nested group inside the form group, where we have a custom validator checking the form group with password and confirmPass, so when either of the fields are changed, the validator is fired, as of previously it only fires when confirmPass field is modified.

So instead do something like this inside the outer formgroup:

// ...
passwords: this.fb.group({
  password: ['', [...]],
  confirmPass: ['', [...]]
}, {validators: this.checkPasswords}) // add a validator for the whole group
// ...

and then the validator could look like this:

checkPasswords: ValidatorFn = (group: AbstractControl):  ValidationErrors | null => { 
  let pass = group.get('password').value;
  let confirmPass = group.get('confirmPassword').value

  return pass === confirmPass ? null : { notSame: true }
}

Showing the validation error could then be done like this:

*ngIf="addEditUserForm.hasError('notSame', 'passwords')"

Of course you don't need to have a nested group, but it's better to not have the custom validator fire every time when any changes happen to the form. This way it's only fired when changes happen to this inner form group.

Answer 3

For those who want to add a custom validator without being forced to pass from the form group validation, it's possible to add the validator after defining the form.

One advantage of this approach is that the error is added to the form control and not to the form group. This way it's more easy to display the error associated to the field since we can check the error directly on the field/form control itself.

This is how I implemented it:

Custom validator

import { AbstractControl, ValidatorFn } from '@angular/forms';

export class MismatchValidator {

  static mismatch(otherInputControl: AbstractControl): ValidatorFn {

    return (inputControl: AbstractControl): { [key: string]: boolean } | null => {
      if (inputControl.value !== undefined
        && inputControl.value.trim() != ""
        && inputControl.value !== otherInputControl.value) {
        return { 'mismatch': true };
      }

      return null;
    };
  }
}

Applying the custom validator to the form control

  ngOnInit() {
    this.initForm();
    // The validators are set after defining the form in order to be able to access the password control and pass it to the custom validator as a parameter
    this.setValidators();
  }

  private initForm() {
    this.myForm = this.formBuilder.group({
      password: new FormControl(''),
      passwordConfirmation: new FormControl('')
    });
  }

  private setValidators() {
    const formValidators = {
      "password": Validators.compose([
        Validators.required,
        //....
      ]),
      "passwordConfirmation": Validators.compose([
        Validators.required,
        MismatchValidator.mismatch(this.myForm.get("password")) 
      ])
    }

    this.passwordRecoveryForm.get("password").setValidators(
      formValidators["password"]
    );
    this.passwordRecoveryForm.get("passwordConfirmation").setValidators(
      formValidators["passwordConfirmation"]
    );
  }

The validators are set after defining the form in order to be able to access the password control and pass it to the custom validator as a parameter.

Answer 4

I had some problems implementing this, and when i got it implemented with a custom validator and errorStateMatcher, i got the problem that the formbuilder.group function were deprecated, but after some inspection I found that my validator had to change to comply to the group function.

The Controller looks like this:

// ...
addEditUserForm: FormGroup;
passwordMatcher = new ComparisonErrorStateMatcher();

constructor(private formBuilder: FormBuilder) {
  this.addEditUserForm = this.formBuilder.group({
    password: ['', Validators.required],
    confirmPass: ['', Validators.required],
  }, { validators: [MatchValidator.validate] }); // add validator to group
}
// ...

My validator looked like this:

export class MatchValidator {
  // (group: AbstractControl) is the form group but needs to be AbstractControl instead of (group: FormGroup) to remove deprecation warning. 
  static validate(group: AbstractControl): ValidationErrors | null { 
    const password = group.get('password')?.value;
    const confirmPassword = group.get('confirmPass')?.value;

    return password === confirmPass ? null : { notMatching: true }
  };
}

And my ErrorStateMatcher looked like this:

export class ComparisonErrorStateMatcher implements ErrorStateMatcher {
  isErrorState(control: FormControl | null, form: FormGroupDirective | NgForm | null): boolean {
    const invalidCtrl = !!(control && control.invalid && control.parent?.dirty);
    const invalidParent = !!(control && control.parent && control.parent.invalid && control.parent.dirty);

    return (invalidCtrl || invalidParent) && (control?.touched ?? false);
  }
}

Lastly the HTML would have to look something like this:

<form [formGroup]="addEditUserForm">

  <mat-form-field >
    <mat-label>password</mat-label>
    <input formControlName="password"
           matInput />
    <mat-error *ngIf="newPasswordForm.hasError('required')">
      password is required
    </mat-error>
  </mat-form-field>

  <mat-form-field>
    <mat-label>confirm password</mat-label>
    <input formControlName="confirmPass"
           [errorStateMatcher]="passwordMatcher"
           matInput />
    <mat-error *ngIf="newPasswordForm.hasError('notMatching')">
      passwords don't match
    </mat-error>
  </mat-form-field>
</form>

This creates a form with two input fields that are required to match.

Answer 5

If you want to do it that way, you need bind the function to the current "this" context. Pass over this.validatePasswordConfirmation.bind(this) but note that this function will be passed the FormControl for the confirmation, and not the FormGroup like you stated in the function signature.

Answer 6

I did a different approach that will work for any control. First I define the basic controls of the form:

    this.myForm = this.formBuilder.group({
            name: ['', Validators.required],
            password: ['', Validators.required],
    });

Then I create a new control to confirm the value with my custom validator:

    const confirmPasswordControl = new FormControl('', {
            validator: sameValueAs(this.myForm, 'password')
    });

    this.myForm.addControl('confirmPassword', confirmPasswordControl);

The code of the sameValueAs validator is as follows, you can define it on a separte file to be used anywhere

export function sameValueAs(group: FormGroup, controlName: string): ValidatorFn {
    return (control: FormControl) => {
          const myValue = control.value;
          const compareValue = group.controls[controlName].value;

          return (myValue === compareValue) ? null : {valueDifferentFrom:controlName};

    };
}

Answer 7

Your answer should work just fine. All you need to do is add .value

Like here:

this.addEditUserForm = this.builder.group({
            firstName: ['', Validators.required],
            lastName: ['', Validators.required],
            title: ['', Validators.required],
            email: ['', Validators.required],
            password: ['', Validators.required],
            confirmPass: ['', [Validators.required, this.validatePasswordConfirmation]]
        });
validatePasswordConfirmation(group: FormGroup): any{
        let valid = true;
         if (this.addEditUserForm.controls.password**.value** != this.addEditUserForm.controls.confirmPass**.value**) {
             valid = false;
           this.addEditUserForm.controls.confirmPass.setErrors({validatePasswordConfirmation: true});
        // }
        return valid;
    }

Answer 8

Using Reactive Forms - I think this is the simple way

change-password.ts

passwordChangeForm = new FormGroup(
    {
      currentPassword: new FormControl("", [
        Validators.required,
        Validators.minLength(6),
      ]),
      newPassword: new FormControl("", [
        Validators.required,
        Validators.minLength(6),
      ]),
      confirmNewPassword: new FormControl("", [
        Validators.required,
        Validators.minLength(6),
      ]),
    },
    {
      validators: (control) => {
        if (control.value.newPassword !== control.value.confirmNewPassword) {
          control.get("confirmNewPassword").setErrors({ notSame: true });
        }
        return null;
      },
    }
  );

change-password.html

<div>
  <h1 mat-dialog-title>Change Password</h1>
  <form [formGroup]="passwordChangeForm">
    <mat-form-field appearance="outline">
      <mat-label>Current Password</mat-label>
      <input matInput formControlName="currentPassword" type="password" />
    </mat-form-field>
    <mat-form-field appearance="outline">
      <mat-label>New Password</mat-label>
      <input matInput formControlName="newPassword" type="password" />
    </mat-form-field>
    <mat-form-field appearance="outline">
      <mat-label>Confirm New Password</mat-label>
      <input matInput formControlName="confirmNewPassword" type="password" />
      <mat-error
        *ngIf="passwordChangeForm.get('confirmNewPassword').hasError('notSame')"
      >
        New Password Doesn't match
      </mat-error>
    </mat-form-field>
  </form>
  <button
    mat-raised-button
    color="primary"
    (click)="changePassword()"
    [disabled]="passwordChangeForm.invalid"
  >
    Change Password
  </button>
</div>

Answer 9

If you don't want to go through a custom validator you can just create a input field that is standalone and therefore will not compute in your formGroup but rather through ngModel

<input type="password" matInput [(ngModel)]="passwordConfirm" [ngModelOptions]="{standalone: true}">

Then in your ts you can just validate and throw error or invalidate the form if you want. Just found it slightly quicker and practical:

// Check Passwords Match

  if (this.staffAccountForm.value.password !== this.passwordConfirm) {
    this.snackbar.snackBarSimple('Passwords do not match.');
    return false;
  }