How can I implement synchronous validators in Angular forms?

How can I implement synchronous validators in Angular forms?

You can implement synchronous validators in Angular by using the built-in validators from @angular/forms. For example, you can use Validators.required, Validators.minLength, and Validators.maxLength.

Can you show me an example of using a custom synchronous validator?

Sure! You can create a custom synchronous validator by defining a function that returns either null (if valid) or an error object (if invalid). Here's a simple example:

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

export function customValidator(control: AbstractControl): ValidationErrors | null {
  const isValid = /* your validation logic */;
  return isValid ? null : { 'customError': true };
}

How do I apply this custom validator to a form control?

You can apply the custom validator when creating the form control. Here's how:

this.form = this.fb.group({
  myControl: ['', [customValidator]]
});

What happens if the validation fails?

If the validation fails, the form control will have an error object, and you can check for errors in your template to display appropriate messages.