How do I make a CORS request with fetch on my localhost? - ajax

Question

I'm building a React/Redux app that integrates with GitHub's API. This app will require users to sign-in using GitHub's OAuth. I'm trying to use the npm package isomorphic-fetch to do the request but cannot seem to get it to work.
Here is the Request:
require('isomorphic-fetch');
var types = require(__dirname + '/../constants/action_types');
module.exports.handleAuthClick = function() {
return function(dispatch, getState) {
var state = getState();
return fetch('http://localhost:3000/auth')
.then(function(res) {
if (res.status <= 200 && res.status > 300) {
// set cookie
// return username and token
return {
type: HANDLE_AUTH_CLICK,
data: res.json()
};
}
throw 'request failed';
})
.then(function(jsonRes) {
dispatch(receiveAssignments(jsonRes));
})
.catch(function(err) {
console.log('unable to fetch assignments');
});
};
};
Here is my Router
authRouter.get('/', function(req, res) {
res.redirect('https://github.com/login/oauth/authorize/?client_id=' + clientId);
});
And here is the Error I keep getting
Fetch API cannot load https://github.com/login/oauth/authorize/?client_id=?myclientID
No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'http://localhost:3000' is therefore not allowed access. If an opaque
response serves your needs, set the request's mode to 'no-cors' to fetch the
resource with CORS disabled.

Answer 1

Looks like this is a security option which prevents a web page from making AJAX requests to different domain. I faced the same problem, and below steps fixed it.
Firstly enable CORS in the WebService app using 'package Manager' console
PM>Install-Package Microsoft.AspNet.WebApi.Cors
Inside App_Start/WebApiConfig.cs file inside the method Register (HttpConfiguration config) add code
config.EnableCors();
Finally add the [EnableCors] attribute to the class
namespace <MyProject.Controllers>
{
[EnableCors(origins: "http://example.com", headers: "*", methods: "*")]
public class MyController : ApiController
{
//some code