Angular 5+ TS2339：类型不存在属性

Question

我有一个示例用户注册/登录Node.js / Angular应用程序在Angular 4上完全正常工作，但在我更新到5.1.0之后它给了我错误。

Express.js函数来验证用户身份：

""

Angular身份验证服务功能：

router.post('/authenticate', (req, res, next) => {
  const username = req.body.username;
  const password = req.body.password;

  User.getUserByUsername(username, (err, user) => {
    if(err) throw err;
    if(!user) {
      return res.json({ success: false, msg:'User not found' });
    }

    User.comparePassword(password, user.password, (err, isMatch) => {
      if(err) throw err;
      if(isMatch) {
        const token = jwt.sign({ data: user }, config.secret, {
          expiresIn: 604800
        });

        res.json({
          success: true,
          token: 'JWT ' + token,
          user: {
            id: user._id,
            name: user.name,
            username: user.username,
            email: user.email
          }
        });
      } else {
        return res.json({ success: false, msg:'Wrong password' });
      }
    });
  });
});

登录组件功能：

authenticateUser(user) {
    let headers = new HttpHeaders();
    headers.append('Content-Type', 'application/json');
    return this.httpClient.post('http://localhost:3002/users/authenticate',
      user, { headers: headers });
  }

错误输出：

onLoginSubmit() {
    const user =  {
      username: this.username,
      password: this.password
    }

    this.authService.authenticateUser(user).subscribe(data => {
      if(data.success) {
        this.authService.storeUserData(data.token, data.user);
        this.flashMessagesService.show('You are now logged in',
          { cssClass: 'alert-success', timeout: 5000 });
        this.router.navigate(['/dashboard']);
      } else {
        this.flashMessagesService.show(data.msg,
          { cssClass: 'alert-danger', timeout: 5000 });
        this.router.navigate(['/login']);
      }
    });
  }