How can I implement async validation in Angular forms using Angular CLI?

How can I implement async validation in Angular forms using Angular CLI?

You can implement async validation in Angular forms by creating a custom validator that returns an observable. Would you like a code example?

Yes, please provide a code example for async validation.

Sure! First, create a validator function that returns an observable. Here's a simple example:

import { AbstractControl, ValidationErrors } from '@angular/forms';
import { of } from 'rxjs';
import { map, delay } from 'rxjs/operators';

export function asyncValidator(control: AbstractControl): Observable<ValidationErrors | null> {
  return of(control.value).pipe(
    delay(1000), // Simulate a server delay
    map(value => {
      return value === 'invalid' ? { asyncInvalid: true } : null;
    })
  );
}

How do I use this validator in my form?

You can use the async validator in your form control like this:

this.myForm = this.fb.group({
  myField: ['', { asyncValidators: [asyncValidator] }]
});