How to send error http response in express/node js?

Question

So in login page I am sending credentials from angular to express through get request.What I wanna do is that if found in database,send response and handle it in angular else if not found in db I want express to send error response and handle it angular error response function but my code isnt working.

Angular controller:

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");           }         );     }   } ]); 

APP.js:

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

Controller:

  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");       }     });   } 

Answer 1

In Node with ExpressJS you can use res.status() to send the error:

return res.status(400).send({    message: 'This is an error!' }); 

In Angular you can catch it in the promise response:

$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             // response.data.message will be "This is an error!"              console.log(response.data.message);              $scope.message = response.data.message         }     ); 

Answer 2

Or use instance of Error class

response.status(code).send(new Error('description'));