POST https://ift.tt/UPdH6I 415 Unsupported Media when using fetch

I'm trying to make a request to get an authorization code from the spotify api using fetch but I keep getting a 415 error code. Any help would be greatly appreciated.

class CodeHandler {
  constructor(Args){
    this._args = Args;
    this.opts = {
       data: {
         name: "test",
         public: "false",
     grant_type: 'authorization_code',
     code: this._args[1],
     redirect_uri: 'http%3A%2F%2Ftest.openjukeboxdev.info%2F'
       },
       headers: {
         'Authorization': 'Basic ZjRmMTk0MTIzOTM3NDgyMmI5Mjg3OGY4YTUzYjUwMjk6MDVlODA3ZDk0NDljNGE1MmFlMzM1YTQxOTlhMjMzYmI'
       }}
  }

  response() {
    console.log(this.opts)
    console.log(JSON.stringify(this.opts))
    return this._args[1];
  }

  getAccessToken(){
    const url = "https://accounts.spotify.com/api/token";

    fetch(url, {
      method: 'post',
      body: JSON.stringify(this.opts)
    })
   .then(function (data) {
      console.log('Request succeeded with JSON response', data);
    })
    .catch(function (error) {
      console.log('Request failed', error);
    }); 
  }
  pausePlayback(){
    const http = new XMLHttpRequest();
    const url = 
    http.open("POST", url);
    http.send();
    alert(http.responseText);
  }
}

This is the full error. I get when I try to make the post request.

Response {type: "cors", url: "https://accounts.spotify.com/api/token", redirected: false, status: 415, ok: false, …}
type: "cors"
url: "https://accounts.spotify.com/api/token"
redirected: false
status: 415
ok: false
statusText: ""
headers: Headers
__proto__: Headers
body: (...)
bodyUsed: false
__proto__: Response