fetch-etag.mjs

var myHeaders = new Headers();
var ETagHeaders = new Headers();
myHeaders.append("x-api-key", "INSERT API KEY");

var requestOptions = {
  method: 'GET',
  headers: myHeaders,
  redirect: 'follow'
};

var rerequestOptions = {
    method: 'GET',
    headers: ETagHeaders,
    redirect: 'follow'
  };
fetch("https://api.crew3.xyz/communities/ambire/leaderboard", requestOptions)
// Fetch the data with the API key
.then(r => ({
    etag: r.headers.get('etag'), 
    json: r.json()
}))
//assign the etag & data to a variable
.then(data => { 
    // print the etag & data
    console.log(data.etag);
    data.json.then(console.log)
    // add the etag to the headers + If-None-Match
    ETagHeaders.append("If-None-Match", data.etag);
    ETagHeaders.append("x-api-key", "ENTER API KEY");
    //fetch with the new headers
    fetch("https://api.crew3.xyz/communities/ambire/leaderboard", rerequestOptions)
    .then(r => ({
        etag: r.headers.get('etag'), 
    }))
    .then(data => { 
        // do something with your etag and data
        console.log(data.etag);
    //  data.json.then(console.log)
    })
})
.catch(console.error.bind(console));