expressjs ldap authentication showing basic auth pop up form - node.js

Question

I'm a newbie to expressjs and ldap.
Need your help with getting my way through the code flow.
I need to authenticate user credentials against ldap server.
I'm using this ldap library https://github.com/vesse/node-ldapauth-fork for making it work.
I get the pop-up form on my broswer that asks for my basic auth credentials after I have submitted the login credentials with the login form(loginCtrl.js).
When i enter the credentials into the popup, the backends sees them as "undefined"
My question is why is the basic auth form popping up, if I'm already sending teh credentials via loginCtrl.js
This is my front end code that calls the REST api
login.html
app.controller("loginCtrl", ["$scope", "$http", "$location","$document", "$uibModal", "$filter", "$q", function($scope, $http, $location, $document, $uibModal, $filter, $q) {
$scope.keepLoggedIn = false;
$scope.login = function() {
var body = {};
body["username"] = $scope.username;
body["password"] = $scope.password;
var auth = window.btoa($scope.username+":"+$scope.password);
console.log(auth);
/* $http.post('/login', JSON.stringify(credentials)).then(function(success){
console.log("success");
}, function(error){
console.error("error");
});*/
var results = [];
$http({
method: 'POST',
headers: {'Authorization': "Basic " + auth},
url: '/login',
data: JSON.stringify(body)
})
.then(function (success) {
console.log(success);
results.push(success);
}, function (error) {
results.push(error.data);
});
}
}]);
<div id="container">
<form ng-submit="login()">
<label for="username">Username:</label>
<input type="text" ng-model="username" id="username" name="username">
<label for="password">Password:</label>
<input type="password" ng-model="password" id="password" name="password">
<div id="lower">
<input type="checkbox" ng-model="keepLoggedIn"><label for="checkbox">Keep me logged in</label>
<input type="submit" value="Login">
</div><!--/ lower-->
</form>
</div>
This is the expressjs server code that uses ldapauth to authenticate against ldap
var express = require('express');
var basicAuth = require('basic-auth');
var LdapAuth = require('ldapauth-fork');
var app = express();
var ldap = new LdapAuth({
url: 'ldap://ldapserver.net:389',
bindDN: 'uid=root,ou=sample,dc=dept,dc=net',
bindCredentials: 'secret',
searchBase: 'ou=sample,dc=dept,dc=net',
searchFilter: '(uid={{username}})',
reconnect: true
});
ldap.on('error', function (err) {
console.error('LdapAuth: ', err);
});
var rejectBasicAuth = function(res) {
res.statusCode = 401;
res.setHeader('WWW-Authenticate', 'Basic realm="Example"');
res.end('Access denied');
}
var basicAuthMiddleware = function(req, res, next) {
ldap.authenticate(req.body.username, req.body.password, function(err, user) {
console.log("callback:"+user);
if (err) {
console.log(err);
return rejectBasicAuth(res);
}
console.log("success");
req.user = user;
next();
});
};
app.post('/login',basicAuthMiddleware, function(req,res){
res.send({"status":"ok"});
});
app.listen(2500, function(){
console.log('Express started on http://localhost:' + 2500 + '; press Ctrl-C to terminate.');
});