How to add uris to post request in javascript

Question

I can't seem to figure out how to add uris to a post request like in this api request: https://developer.spotify.com/console/post-playlist-tracks/?playlist_id=3cEYpjA9oz9GiPac4AsH4n&position=&uris=spotify%3Atrack%3A4iV5W9uYEdYUVa79Axb7Rh%2Cspotify%3Atrack%3A1301WleyT98MSxVHPZCA6M

this is what my request looks like currently put does not work

fetch(endPoint, {
method: "POST",
headers: {
  Authorization: `Bearer ${access_token}`,
},
body: JSON.stringify({
  "uri": data
})
});

thanks in advance for any help