how to validation form in angular on submit code example

Example 1: formgroup check if valid

form: FormGroup;

onSubmit(){
    //checks if form is valid
       if( this.form.valid){
          //more code here
        }
}

Example 2: angular9+how+to+add+validators

this.form.controls["firstName"].setValidators([Validators.minLength(1), Validators.maxLength(30)]);