Node.js 如何在 expressnode js 中发送错误 http 响应

所以在登录页面中，我通过get请求从angular向express发送凭据.我想做的是，如果在数据库中找到，发送响应并在angular中处理它，否则如果在db中找不到，我希望express发送错误响应并处理它angular error response函数，但我的代码不起作用.

Angular 控制器:

myapp.controller('therapist_login_controller', ['$scope', '$localStorage', '$http',
  function($scope, $localStorage, $http) {
    $scope.login = function() {
      console.log($scope.username + $scope.password);
      var data = {
        userid: $scope.username,
        password: $scope.password
      };
      console.log(data);
      $http.post('/api/therapist-login', data)
        .then(
          function(response) {
            // success callback
            console.log("posted successfully");
            $scope.message = "Login succesful";
          },
          function(response) {
            // failure callback,handle error here
            $scope.message = "Invalid username or password"
            console.log("error");
          }
        );
    }
  }
]);

应用程序.js:

  app.post('/api/therapist-login', therapist_controller.login);

控制器:

  module.exports.login = function(req, res) {

    var userid = req.body.userid;
    var password = req.body.password;
    console.log(userid + password);

    Credentials.findOne({
      'userid': [userid],
      'password': [password]
    }, function(err, user) {
      if (!user) {
        console.log("logged err");
        res.status(404); //Send error response here
        enter code here
      } else {
        console.log("login in");
      }
    });
  }