title: How to send CORS request from React?
body: <p>I have problem with sending CORS request with token in header.
  Fetch code:</p>
  
  <pre><code>fetchApi() {
      fetch('http://some-link.com',
      {
          headers: {
            'Accept': 'application/json',
            'auth-token': 'xxxxxxxxx'
          },
          method: "GET"
      }).then(response =&gt; response.json())
          .then(function(response){
              this.setState({hits:response});
          }).catch(function(error) { console.log(error); });
  
          console.log(this.state.hits);
  };
  </code></pre>
  
  <p>Console log:
  Access to fetch at '<a href="http://some-link.com" rel="nofollow noreferrer">http://some-link.com</a>' from origin '<a href="http://localhost:3000" rel="nofollow noreferrer">http://localhost:3000</a>' has been blocked by CORS policy: Request header field auth-token is not allowed by Access-Control-Allow-Headers in preflight response.</p>
  
  <p>Network request log:</p>
  
  <pre><code>General
  Request URL: http://some-link.com
  Request Method: OPTIONS
  Status Code: 200 OK
  Remote Address: some_ip:80
  Referrer Policy: no-referrer-when-downgrade
  
  Response Headers
  Access-Control-Allow-Headers: origin, x-requested-with, content-type, auth_token
  Access-Control-Allow-Methods: POST, GET, PUT, DELETE, OPTIONS
  Access-Control-Allow-Origin: *
  Cache-Control: no-cache, private
  Connection: Keep-Alive
  Content-Length: 8
  Content-Type: application/json
  Date: Tue, 13 Nov 2018 13:30:35 GMT
  Keep-Alive: timeout=5, max=100
  Server: Apache/2.4.10 (Debian)
  
  Request Headers
  Provisional headers are shown
  Access-Control-Request-Headers: auth-token
  Access-Control-Request-Method: GET
  Origin: http://localhost:3000
  Referer: http://localhost:3000/
  User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36
  </code></pre>
  
  <p>Any ideas what might be wrong?</p>