RegEx Validator angular

regex.ts

emailRegex = /^[a-z0-9!#$%&'+\/=?^_`{|}~.-]+@[a-z0-9]([a-z0-9-][a-z0-9])?(.a-z0-9?)*$/i;
registration : FormGroup;
constructor(r: FormBuilder, public http :Http){
this.registration = r.group({
  'chosen_username' : [null, Validators.required],
  'chosen_email' : [null, Validators.pattern(this.emailRegex)],
  'chosen_password' : [null, Validators.required],
  });
}