CORS 仅放置请求的预检问题

Question

I am having a weird issue. I get cors error for put request on browser:

Access to fetch at 'http://localhost:3015/pathtest/api/v1/results/cc7637578fad1a6fcfb4249fbf000a13/load' from origin 'https://localhost:9444' has been blocked by CORS policy: Method PUT is not allowed by Access-Control-Allow-Methods in preflight response.

And here is my code to enable cors in backend(nodejs). All the other api requests have been fixed with the below code and only put still returns cors issue:

app.use(function(req, res, next) {
  // res.header("Access-Control-Allow-Origin", "*");
  // res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  // res.header('Access-Control-Allow-Methods', 'PATCH, PUT, POST, GET, DELETE, OPTIONS');
  //     // allow preflight
  //     if (req.method === 'OPTIONS') {
  //       res.send(200);
  //   } else {
  //       next();
  //   }

  res.header('Access-Control-Allow-Origin', '*');
res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,PATCH,OPTIONS');
res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization, Content-Length, X-Requested-With');
// allow preflight
if (req.method === 'OPTIONS') {
    res.send(200);
} else {
    next();
}
});

Am I missing anything?

**Update

Answer 1

From both of our investigation through comments, we've figured out that this was the cause of your problem...

The screenshot you show illustrates that the middleware code you show in your question is not handling that request. That apparently means you have some other middleware before it that is taking over the request and that one is not doing what you want so it's getting in the way of the middleware you do want to handle the request.

If, in your search for a solution, you've put something like app.use(cors()) (or some other code that attempts to handle CORs requests) into your code and that's before your own custom middleware, then it getting in the way of your own middleware. Remove that other CORS-related middleware so your custom middleware can get unimpeded access to the incoming requests and can do its job.

Remember that middleware and other request handlers are run in the order they were registered and if a given handler sends a response and does not call next() , then no more request handlers/middleware in the chain will get to act on that request.