Form status
- valid: This property returns true if the element’s contents are valid and false otherwise.
- invalid: This property returns true if the element’s contents are invalid and false otherwise.
- pristine: This property returns true if the element’s contents have not been changed.
- dirty: This property returns true if the element’s contents have been changed.
- untouched: This property returns true if the user has not visited the element.
- touched: This property returns true if the user has visited the element.

this.contactForm = this.formBuilder.group({
  firstname: ['', [Validators.required, Validators.minLength(10)]],
  lastname: ['', [Validators.required, Validators.maxLength(15), Validators.pattern("^[a-zA-Z]+$")]],
  email: ['', [Validators.required, Validators.email]],
  gender: ['', [Validators.required]],
  address: this.formBuilder.group({
    city: ['', [Validators.required]]
  })
});

  get firstname() {
    return this.contactForm.get('firstname');
  }

 this.filterForm.controls['textSearch'].valueChanges
      .pipe(
        debounceTime(500),
        distinctUntilChanged()
      )
      .subscribe(textSearch => {
        console.log(textSearch)
      });

import { Subject } from 'rxjs';

private unsubscribe: Subject<any>;

constructor() {
  this.unsubscribe = new Subject();
}

ngOnDestroy(): void {
  this.unsubscribe.next();
  this.unsubscribe.complete();
}

Template form  :   " ___ "
pattern = "regex_string"

Reactive form  : / ___  /
Validators.pattern(/^(?=[^A-Z]*[A-Z])(?=[^a-z]*[a-z])(?=\D*\d).{8,}$/)   

((^\s*((([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]))\s*$)|(^\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))(%.+)?\s*$))