岗位http://localhost:3000/api/signup400(错误请求）

我是MEAN堆栈的新手，在通过http.post.发送注册数据时遇到了问题

这是我的服务器代码：

var express = require('express'),
  bodyParser = require('body-parser'),
  methodOverride = require('method-override'),
  errorHandler = require('express-error-handler'),
  morgan = require('morgan'),
  routes = require('./routes'),
  api = require('./routes/api'),
  http = require('http'),
  path = require('path'),
  usersController = require('./public/js/userscontroller.js');
var app = module.exports = express();
var mongoose = require('mongoose');
var connection = require('./config/database')(mongoose);
var models = require('./models/models')(connection);
var cons = require('consolidate');

/**
 * Configuration
 */
// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/views');
app.engine('html', cons.swig);
app.set('view engine', 'html');
app.use(morgan('dev'));
app.use(bodyParser.json());
app.use(methodOverride());
app.use(express.static(path.join(__dirname, 'public')));
var env = process.env.NODE_ENV || 'development';
// development only
if (env === 'development') {
  app.use(errorHandler());
}
// production only
if (env === 'production') {
  // TODO
}

/**
 * Routes
 */
// serve index and view partials
app.get('/', routes.index);
app.get('/partials/:name', routes.partials);
// JSON API
app.post('/api/signup', api.signup);
// redirect all others to the index (HTML5 history)
app.get('*', routes.index);

/**
 * Start Server
 */
http.createServer(app).listen(app.get('port'), function () {
  console.log('Express server listening on port ' + app.get('port'));
});

这是我的api：

/*
 * Serve JSON to our AngularJS client
 */
var User = require('../models/user');

exports.name = function (req, res) {
  res.json({
    name: 'Bob'
  });
};

exports.signup = function (req, res, next){
    console.log("in signup in API");
    if(!req.body.username || !req.body.password){
        return res.status(400).json({message: 'Please fill out all feelds'});
    }
    var user = new User();
    user.username = req.body.username;
    user.setPassword(req.body.password);
    console.log("after set password");
    user.save(function(err, result) {
        if(err){return next(err); }
        res.json(result);
    });
};

这是我的客户端JS app.JS:

'use strict';
// Declare app level module which depends on filters, and services
angular.module('myApp', [
  'myApp.controllers',
  'myApp.filters',
  'myApp.services',
  'myApp.directives',
  'ngResource'
]).
config(function ($routeProvider, $locationProvider) {
  $routeProvider.
    when('/view1', {
      templateUrl: 'partials/partial1',
      controller: 'usersController'
    }).
    when('/view2', {
      templateUrl: 'partials/partial2',
      controller: 'usersController'
    }).
    otherwise({
      redirectTo: '/view1'
    });
  $locationProvider.html5Mode(true);
}).
factory('auth', ['$http', '$window', function($http, $window, auth){
  var auth = {};
  //saves token
  auth.saveToken = function (token){
    $window.localStorage['nicerpg-token'] = token;
  };
  //Attempts to register the user
  auth.signup = function(user){
    console.log(user);
    $http({
      method: "POST",
      url: "/api/signup",
      headers: {"Content-Type": "application/json"}
    });
    // return $http.post('/api/signup', user).success(function(data){
    //   //auth.saveToken(data.token);
    // });
  };
  return auth;
}]);

最后，这里是controllers.js:

'use strict';
/* Controllers */
angular.module('myApp.controllers', []).
  controller('AppCtrl', function ($scope, $http) {
    $http({
      method: 'GET',
      url: '/api/name'
    }).
    success(function (data, status, headers, config) {
      $scope.name = data.name;
    }).
    error(function (data, status, headers, config) {
      $scope.name = 'Error!';
    });
  }).
  controller('usersController', ['$scope', '$resource', 'auth', function ($scope, $resource, auth) {
    // write Ctrl here
    var User = $resource('/api/users');
    var Signup = $resource('/signup');
      //Gets all the users
    User.query(function(results) {
      //console.log(results);
      $scope.users = results;
    });
    $scope.signup = function(){
      auth.signup($scope.registerform);
      // .error(function(error){
      //   console.log(error);
      //   $scope.error = error;
      // }).then(function(){
      // });
      User.query(function(results) {
        // console.log(results);
        $scope.users = results;
      });
      $scope.registerform = '';
    };
  }]);

当我将localhost:3000/api/signup放入浏览器时，我得到了预期的缺失字段响应；然而，当我尝试使用http.post运行代码时，它会返回400个错误的请求。我已经尝试过多次更改http标头内容类型，但都没有成功，还有许多其他解决方案的尝试都没有成功。请帮帮我：（

谢谢！