数组查找，无法读取未定义的属性长度

Question

如何检查没有长度的选项？有些options估计options，另一些则没有。

当我检查options.length == 0

时，以下代码错误

const { group, data, year } = args;
return (
    data
        .find(element => {
            return element.id == year;
        })
        .options.find(element => {
            return element.id == group;
        }).options.length == 0

数据：

years: [
        {
            label: "Year 3",
            id: 1,
            options: [
                {
                    label: "Firm 01",
                    id: "xxx@xx.co.uk"
                },
                {
                    label: "Firm 02",
                    id:
                        "xxx.co.xxx@group.calendar.google.com"
                }, ....

Answer 1

我认为最好的方法是检查是否定义了变量，可以通过以下方式实现：

class SplashPresenter extends BasePresenter<SplashView> {

   private Scheduler mMainThread;

   private Scheduler mNewThread;

   private UserAuthService userAuthService;

  @Inject
  SplashPresenter(SplashView view, UserAuthService userAuthService, @Named(ValueConstants.NEW_THREAD) Scheduler newThread,  @Named(ValueConstants.MAIN_THREAD) Scheduler mainThread) {
        super(view);
        this.userAuthService = userAuthService;
        mNewThread = newThread;
        mMainThread = mainThread;
  }

让我知道这是否对您有用。