Spotify.NET/SpotifyAPI.Web.Auth/Resources/auth_assets/main.js

function getUrlParams(hash, start) {
  const hashes = hash.slice(hash.indexOf(start) + 1).split('&')

  if (!hashes || hashes.length === 0 || hashes[0] === "") {
    return undefined;
  }

  const params = {}
  hashes.map(hash => {
    const [key, val] = hash.split('=')
    params[key] = decodeURIComponent(val)
  })
  return params
}

function handleImplicitGrant() {
  const params = getUrlParams(window.location.hash, '#');
  if (!params) {
    return;
  }
  params.request_type = "token";

  console.log("Sent request_type token to server", params);
  fetch('?' + new URLSearchParams(params).toString(), {
    method: 'POST',
  });
}
handleImplicitGrant();

function handleAuthenticationCode() {
  const params = getUrlParams(window.location.search, '?');
  if (!params) {
    return;
  }
  params.request_type = "code";

  console.log("Sent request_type code to server", params);
  fetch('?' + new URLSearchParams(params).toString(), {
    method: 'POST',
  });
}
handleAuthenticationCode();