当我通过react应用发出请求时，我的网络服务器会发送404，但是当我直接通过chrome或postman访问它时，我的服务器工作正常

Question

My web server is working fine when I call it through chrome. However when I am using fetch or axiom in my react-app to call the same url, it returns 404 Not Found. The react-app also sends a options request to same url which returns status 200. I have even set this header to allow the origin.

app.use(async (ctx, next) => {
    var origin = ctx.headers.origin;
    ctx.set({
        'Access-Control-Allow-Headers': 'authorization,Content-Type,refresh',
        'Access-Control-Allow-Methods': "GET,HEAD,POST,PUT,DELETE",
        'Access-Control-Allow-Origin': '*',
        'Connection': 'keep-alive',
        'Access-Control-Allow-Credentials': true
    });
    await next();
    console.log('______________')
  });

require('./routes')(app); //2

my ./routes.js file contain

//router.post('/signin' , signinController.signin);
router.get('/signin' , signinController.signin);

can you please tell me what I am missing here. My axios call

axios.get('http://localhost:3002/signin')
              .then(function (response) {
                console.log(response);
              })
              .catch(function (error) {
                console.log(error);
              });

Answer 1

Alright I tried your code out and it works for me if I use app.use(router.allowedMethods()) middleware to pass preflights, OR declare separate option-routes for each route; Or instead of using router.get() there is router.all('/signin', ...) which will also catch options-requests.

This is my complete server code:

const app = new Koa();

const router = new Router();

router.get('/signin' , (ctx, next) => {
  ctx.body = '{"status":"hello"}';
});

// Adding a options-route works (instead of router.allowedMethods())
router.options('/signin' , (ctx, next) => {
  ctx.body = '';
});

app.use(async (ctx, next) => {
  var origin = ctx.headers.origin;
  ctx.set({
    'Access-Control-Allow-Headers': 'authorization,Content-Type,refresh',
    'Access-Control-Allow-Methods': "GET,HEAD,POST,PUT,DELETE",
    'Access-Control-Allow-Origin': '*',
    'Connection': 'keep-alive',
    'Access-Control-Allow-Credentials': true
  });
  await next();
  console.log('______________')
});

app.use(router.routes());
// app.use(router.allowedMethods()); // This works instead of separate option-routes.
app.use((ctx, next) => {
  console.log('here');
  next();
});


app.listen(9787);

And this is my call:

axios.defaults.headers.common['Authorization'] = "sometoken";
axios.get('http://localhost:9787/signin').then(response =>{
  console.log(response); // {data: {…}, status: 200, ... }
});

(I had to add the header or the CORS won't trigger.)

I've tried setting various origin and headers and it does obey your middleware. But I did notice that if you choose to use allowedMethods() , that will override your Access-Control-Allow-Methods (and make it useless).

Answer 2

It has to do with cross origin support

You can use this package @koa/cors@2 to add cors support

const Koa = require('koa');
const cors = require('@koa/cors');

const app = new Koa();
app.use(cors());

Heres the link to the package https://github.com/koajs/cors