The implementation has been done to my best of knowledge and also research the web for standard pseudocode yet I keep getting error. Please take a look.

HMAC IMPLEMENTATION FOR BITAPS API ENDPOINT

// import the useful packages
const crypto = require('crypto');
const sha256 = require('sha256');

// defining the variables
let nonce = crypto.randomBytes(16).toString('base64');
let key = sha256.x2(WALLET_ID + WALLET_PASSWORD); // to double hash
let msg = WALLET_ID + nonce;

let headers = { // will be properly defined soon
    "Access-Nonce": nonce,
    "Access-Signature": HMAC_signature
}

// create the hmac util here
function HMAC(key, msg) {
    let hmac = crypto.createHmac('sha256', key);

    hmac.update(msg, 'utf8');
    return hmac.digest();
}

// Signing the get requesst with HMAC keys
let HMAC_signature = HMAC(key, msg);