CORS Error: It does not have HTTP ok status-CodePudding

I am currently building a back-end server using express.js. It was working fine until I got this problem with the web based version of my project:

Access to XMLHttpRequest at 'myurl.net/' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

Strangely enough, I can access the back-end server from the app version written with Kotlin without any problems and make POST, GET requests. What am I doing wrong now?

In the front-end server I develop with React.JS, the request looks like this: (JavaScript)

axios.post("myurl.net/", {
  email: "[email protected]",
  password: "mypassword",
  newuser: "false"
}).then(function (res) {
  console.log(res)
}).catch(function (error) {
  console.log(error)
})

The Express Server looks like this (I have reduced it to a single request to make it clearer):

require("dotenv").config();
const express = require("express");
const listen = require("./listen")
const bodyParser = require("body-parser");

const service = express();

service.use(bodyParser.urlencoded({ extended: false }));
service.use(bodyParser.json());
service.set("view engine", "ejs")

service.all('/*', function(req, res, next) {
    res.setHeader("Access-Control-Allow-Origin", "*");
    res.setHeader("Access-Control-Allow-Credentials", "false");
    res.setHeader("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT");
    res.setHeader("Access-Control-Allow-Headers", "Access-Control-Allow-Headers, Origin,Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers");
    next();
});

service.post("/", async (req, res) => {
    if(req.body.test == "hello_world") {
        res.json({
            server: "hello"
        })
    }
})

listen(service)

By the way, locally the back-end server works strangely, on the server with a domain and HTTPS then somehow not.

CodePudding user response：

Pay close attention to the error message:

Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

Then look up preflight request:

It is an OPTIONS request, using three HTTP request headers: Access-Control-Request-Method, Access-Control-Request-Headers, and the Origin header.

You don't have a handler for service.options("/" so it 404s.

You need to respond with a 200 OK status.

I strongly recommend the use of the cors middleware package which will take care of this for you.