Requests to an API with JavaScript not being authenticated

I’ve been tinkering with a similar issue for the past few days and here is a solution I came up (full credit to Julli4n on Github for the bat generation code)

javascript:(

function(){

function arrayBufferToBase64String(arrayBuffer){
    let res = "";
    const bytes = new Uint8Array(arrayBuffer);
    for (let i = 0; i < bytes.byteLength; i++) {
        res += String.fromCharCode(bytes[i]);
    };
    return btoa(res);
};
async function hashStringSha256(str){
    const uint8 = new TextEncoder().encode(str);
    const hashBuffer = await crypto.subtle.digest("SHA-256", uint8);
    return arrayBufferToBase64String(hashBuffer);
};

async function signWithKey(privateKey, data){
    const bufferResult = await crypto.subtle.sign(
        {name: "ECDSA",hash: { name: "SHA-256" }},
        privateKey,
        new TextEncoder().encode(data).buffer
    );
    return arrayBufferToBase64String(bufferResult);
};

async function getCryptoKeyPairFromDB(dbName,dbObjectName,dbObjectChildId){
    let targetVersion = 1;
    /*we want Roblox to create the DB on their end, so we do not want to interfere*/
    if ("databases" in indexedDB) {
        const databases = await indexedDB.databases();
        const database = databases.find((db) => db.name === dbName);
        if (!database) {
            return null;
        }
        if (database?.version) {
            targetVersion = database.version;
        }
    };
    return new Promise((resolve, reject) => {
        const request = indexedDB.open(dbName,targetVersion);
        request.onsuccess = () => {
            try {
                const db = request.result;
                const transaction = db.transaction(dbObjectName, "readonly");
                const objectStore = transaction.objectStore(dbObjectName);
                const get = objectStore.get(dbObjectChildId);
                get.onsuccess = () => {
                    resolve(get.result);
                };
                get.onerror = () => {
                    reject(request.error);
                };
                transaction.oncomplete = () => {
                    db.close();
                };
            } catch (err) {
                reject(err);
            }
        };
        request.onerror = () => {
            reject(request.error);
        }
    })
};


async function generateBAT(body){
        const pair = await getCryptoKeyPairFromDB("hbaDB","hbaObjectStore","hba_keys");
        
        if (!pair?.privateKey) {
            return null;
        };
        const timestamp = Math.floor((Date.now()+1000) / 1000).toString();
        let strBody;
        if (typeof body === "object") {
            strBody = JSON.stringify(body);
        } else if (typeof body === "string") {
            strBody = body;
        };

        const hashedBody = await hashStringSha256(strBody);
        const payloadToSign = [hashedBody, timestamp].join("|");
        const signature = await signWithKey(pair.privateKey, payloadToSign);

        return [hashedBody, timestamp, signature].join("|");
    };


/*-------------*/

token = document.getElementsByName("csrf-token")[0].dataset.token;

body = "";
obody = "";

headers = {
    "x-csrf-token":token,
    "x-bound-auth-token" : "",
    "accept":"application/json"};

bat = generateBAT(body);
bat.then((tok) => {
headers["x-bound-auth-token"] = tok
});
  
const fetchPromise = fetch("https://economy.roblox.com/v1/user/currency",
  {"headers":headers,
  "method":"GET",
  "credentials": "include"}
);

fetchPromise
  .then((response) => {
    if (!response.ok) {
        heastr = "";
        
        token = response.headers.get("x-csrf-token");
      throw new Error(`HTTP error: ${response.status+response.statusText}`);
    };
    return response.json();
  })
  .then((data) => {
    alert(JSON.stringify(data));
  })
  .catch((error) => {
    alert(`Could not get... anything: ${error}`);
    alert(JSON.stringify(headers));
    alert(body);
  });

}());

Requests on Roblox that require user authentication now need a bat token in the headers, this is part of a new Roblox update to increase account security, read more about it here