How can I implement advanced features in Angular Reactive Forms?

How can I implement advanced features in Angular Reactive Forms?

You can implement advanced features like custom validators, dynamic form controls, and reactive form arrays. Would you like to know more about any specific feature?

Yes, tell me about custom validators.

Custom validators allow you to create your own validation logic. You can define a function that returns either null if valid or an error object if invalid. Would you like a code example?

That would be great! Please provide a code example.

Sure! Here's a simple custom validator for checking if a control's value is a specific length:

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

export function lengthValidator(length: number): ValidatorFn {
  return (control: AbstractControl): ValidationErrors | null => {
    return control.value && control.value.length !== length ? { 'lengthError': true } : null;
  };
}

You can then use this validator in your form control.