javascript - Angular 构造函数中未定义的“push”

Question

仍在学习 Angular。当尝试在构造函数内填充数字数组时看到这一点

Error: Uncaught (in promise): TypeError: Cannot read property 'push' of undefined

尝试像这样在我的构造函数中填充数组

export class RegisterComponent implements OnInit {
  @Output() cancelRegister = new EventEmitter();
  user: User;
  registerForm: FormGroup;
  bsConfig: Partial <BsDatepickerConfig> ;
  emailErrorMessage: string;
  userErrorMessage: string;
  currentYear: number = new Date().getFullYear();
  startYear = this.currentYear - 120;
  years: number[];


  constructor(private authService: AuthService, private router: Router,
    private alertify: AlertifyService, private fb: FormBuilder) {
    for (let i = this.currentYear; i > this.startYear; i--) {
      this.years.push(i);
    }
  }

Answer 1

您必须初始化类的属性。

export class RegisterComponent implements OnInit {
 ...
 years: number[] = [];
 ...