Мое обязательное поле в моей форме HTML не работает

public validateForm() {
  if (newPerson.surname === null || 
  newPerson.surname === undefined || newPerson.surname === " ")
  {
    error.surname = "Surname is required";
  }
  if (newPerson.age === null || 
  newPerson.age === undefined || newPerson.age === " ")
  {
    error.age = "Age is required";
  }
  if (newPerson.occupation === null || 
  newPerson.occupation === undefined || newPerson.occupation === " ")
  {
    error.occupation = "Occupation is required";
  }
  
  if (newPerson.surname !== null || 
  newPerson.surname !== undefined || newPerson.surname !== " " ||
  newPerson.age !== null || 
  newPerson.age !== undefined || newPerson.age !== " " ||
  newPerson.occupation !== null || 
  newPerson.occupation !== undefined || newPerson.occupation !== "
  )
  {
    this.add();
  }

}

  <div class = "mb-3">
      <label class = "form-label">Enter surname:</label>
      <input type = "text" class = "form-control" placeholder = "Person surname" ng-model= "newPerson.surname" required>
    </div>
    <span *ngIf = "error.surname"> {{error.surname}}</span>
    <div class = "mb-3">
      <label class = "form-label">Enter age:</label>
      <input type = "text" class = "form-control" placeholder = "Person age" ng-model= "newPerson.age" required>
    </div>
    <span *ngIf = "error.age"> {{error.age}}</span>
    <div class = "mb-3">
      <label class = "form-label">Enter occupation:</label>
      <input type = "text" class = "form-control" placeholder = "Person occupation" ng-model= "newPerson.occupation" required>
    </div>
    <span *ngIf = "error.occupation"> {{error.occupation}}</span>
    <button type = "submit" class = "btn btn-primary" ng-click = "validateForm()">Add</button>
    
</form>