subtleHmacSha256.js

(async (secret, body) => {
  let enc = new TextEncoder("utf-8");
  let algorithm = { name: "HMAC", hash: "SHA-256" };

  let key = await crypto.subtle.importKey("raw", enc.encode(secret), algorithm, false, ["sign", "verify"]);
  let signature = await crypto.subtle.sign(algorithm.name, key, enc.encode(body));
  
  let hexString = Array.from(new Uint8Array(signature)).map(byte => byte.toString(16).padStart(2, '0')).join('');

  console.log(hexString);
})("my secret and secure key", "input message");