title: Spotify API Post Request Add Tracks To Playlist - ERROR 400 BAD REQUEST
body: <p>Im having what seems to be a very common error when working on the Spotify API adding tracks to a users playlist. In a previous fetch method I have obtained the users playlistId and am now trying to post tracks onto that playlist with that playlistId. I have followed the documentation but am obviously missing something, here is code: </p>
  
  <pre><code>    `        //userUd, playlistId, currentUserAccessToken, trackURIs are all defined 
  
  fetch(`https://api.spotify.com/v1/users/${userId}/playlists/${playlistId}/tracks`, {
              headers: {
                'Authorization': 'Bearer ' + currentUserAccessToken
              },
              contentType: 'application/json',
              method: 'POST',
              body: JSON.stringify({
                "uris": `[${trackURIs}]`
              })
            }).then(success =&gt; {
              return success;
            }).catch(err =&gt; {
              console.log('here is your error', err);
            })`
  </code></pre>
  
  <p>I did the GET request to authorize user - included scope for creating public playlist, in different code block which is working, here's that:</p>
  
  <p>`let scopes = 'playlist-modify-public';</p>
  
  <p>window.location.replace(<code>https://accounts.spotify.com/authorize?client_id=${clientID}&amp;scope=${scopes}&amp;redirect_uri=${redirectURI}&amp;response_type=token</code>);`</p>
  
  <p>Thanks a ton! </p>