Validate JWS/JWT in nodejs/node

index.js

import { createPublicKey, createVerify } from 'node:crypto'

const [header, payload, signature] = token.split('.').map((tokenPart, index) => {
    const decoded = Buffer.from(tokenPart, 'base64url').toString();
    return index < 2 ? JSON.parse(decoded) : decoded;
  })

const key = (await fetch(`${payload.iss}/.well-known/openid-configuration`)
  .then((res) => res.json())
  .then((config) => fetch(`${config['jwks_uri']}`))
  .then((res) => res.json())
  .catch((error) => console.error('Error while fetching JWKS', error)))
}
).keys[0]

const pubKey = createPublicKey({ key, format: 'jwk' });
const verify = createVerify('RSA-SHA256'); // if header.alg: 'RS256' doesn't work for HMAC
verify.update(`${token.split('.')[0]}.${token.split('.')[1]}`);
const isValid = verify.verify(pubKey, Buffer.from(token.split('.')[2], 'base64url'));