Javascript 如何使用ngx translate转换ts文件中的变量

我想翻译标题、标题和副标题，但不断收到错误消息：

“未捕获的TypeError:无法对“未定义”的属性“heading”进行分解，因为它是未定义的”

---

combineLatest([this._preLoginSvc.sessionExpired$, this._preLoginSvc.passwordCheck$]).pipe(
      first(),
      map(([expired, validPassword]) => {
        headingTitle = this._translateSvc.instant('loginAndPreLoginPage.header');
        if (expired) {
          return {
            heading: headingTitle,
            title: 'Your session expired',
            subTitle:
              'We want to keep your account secure, so we’ve logged you out as the page was inactive for too long. ' +
              'Please sign back in below.'
          };
        } else if (validPassword) {
          return {
            heading: headingTitle,
            title: 'Your password is set',
            subTitle: 'Your password has been set, you can now sign in below.',
          };
        }
        return {
          heading: headingTitle,
          title: 'Enter your details'
        };
      }),
      tap(() => {
        this._preLoginSvc.passwordSet(false);
        this._preLoginSvc.sessionExpired(false);
      }),
    ).subscribe((headings) => this._preLoginSvc.setupDisplay(headings));