Angularjs 如何对付。。凭证标志为'；正确'；CORS错误

我正在运行一个ionic应用程序，该应用程序连接到正在运行的express后端

像往常一样，我面临着CORS问题。在chrome中禁用Web安全性没有帮助

chrome报告的错误是：

(index):1 XMLHttpRequest cannot load http://localhost:3000/auth/facebook. 
Response to preflight request doesn't pass access control check:
Credentials flag is 'true', 
but the 'Access-Control-Allow-Credentials' header is ''. 
It must be 'true' to allow credentials. 
Origin 'http://localhost:8100' is therefore not allowed access.


Remote Address:[::1]:3000
Request URL:http://localhost:3000/auth/facebook
Request Method:OPTIONS
Status Code:200 OK

Response Headers
view source
Access-Control-Allow-Headers:accept, content-type
Access-Control-Allow-Methods:POST
Access-Control-Allow-Origin:http://localhost:8100
Access-Control-Max-Age:31536000
Connection:keep-alive
Content-Length:2
Content-Type:text/plain; charset=utf-8
Date:Wed, 04 Nov 2015 02:25:07 GMT
ETag:W/"2-d736d92d"
X-Powered-By:Express


Request Headers
view source
Accept:*/*
Accept-Encoding:gzip, deflate, sdch
Accept-Language:en-US,en;q=0.8
Access-Control-Request-Headers:accept, content-type
Access-Control-Request-Method:POST
Connection:keep-alive
DNT:1
Host:localhost:3000
Origin:http://localhost:8100
Referer:http://localhost:8100/

第一个问题是： 我在请求头中没有看到任何Access Control Allow Credentials标志，那么为什么chrome会抱怨呢

第二个问题：

---

我尝试过使用CORS express模块，但没有帮助。如何克服这个问题？

我通过在nodejs服务器中包含以下中间件解决了这个问题

var app = express();
app.use(methodOverride());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({
  extended: true
}));

app.use(accessControl);

其中函数accessControl如下所示：

function(req, res, next) {

  var oneof = false;

  if (req.headers.origin) {
    res.header('Access-Control-Allow-Origin', req.headers.origin);
    oneof = true;
  }
  if (req.headers['access-control-request-method']) {
    res.header('Access-Control-Allow-Methods', req.headers['access-control-request-method']);
    oneof = true;
  }
  if (req.headers['access-control-request-headers']) {
    res.header('Access-Control-Allow-Headers', req.headers['access-control-request-headers']);
    oneof = true;
  }
  if (oneof) {
    res.header('Access-Control-Max-Age', 60 * 60 * 24 * 365);
  }

  if (req.originalUrl === '/auth/signup') {
    res.header('Access-Control-Allow-Credentials', true);
  }

  if (req.originalUrl === '/auth/login') {
    res.header('Access-Control-Allow-Credentials', true);
  }

  // intercept OPTIONS method
  if (oneof && req.method === 'OPTIONS') {
    res.sendStatus(200);
  }

  else {
    next();
  }
};

---

这不是一个优雅的解决方案，但它对我起了作用（至少在我找到更好的解决方案之前）

你能自己找到答案吗？如果是这样的话，请写下答案，这样像我这样的人可以从中受益（X）@RicardoPanaggio。。答复张贴