use browser subtle crypto to sign some text with hmac-sha1

cryptoSign.js

async function cryptoSign(message) {
  const key = await window.crypto.subtle.generateKey(
    {
      name: "HMAC",
      hash: { name: "SHA-512" },
    },
    true,
    ["sign", "verify"]
  );
  const encodedText = new TextEncoder().encode(message);
  const signature = await window.crypto.subtle.sign("HMAC", key, encodedText);
  const signatureText = btoa(String.fromCharCode(...new Uint8Array(signature)));
  return signatureText;
}