create-verify-jwt-example.js

const crypto = require('crypto');

function createHash(text, key) {
  return crypto.createHmac('sha256', key).update(text).digest('base64');
}

function createJwt(payload, key) {
  const head = Buffer.from(JSON.stringify({alg: "HS256", typ: "JWT"})).toString('base64');
  payload = Buffer.from(JSON.stringify({
    ...(payload || {}),
    exp: new Date().getTime() + 180000
  })).toString('base64');
  const sign = createHash(`${head}.${payload}`, key);
  return `${head}.${payload}.${sign}`;
}

function checkJwt(jwt, key) {
  const splitJwt = jwt.split('.');
  if (splitJwt.length === 3) {
    try {
      if (createHash(`${splitJwt[0]}.${splitJwt[1]}`, key) === splitJwt[2]) {
        const payload = JSON.parse(Buffer.from(splitJwt[1], 'base64').toString());
        return parseInt(payload.exp) > new Date().getTime();
      }
    } catch (ignore) {}
  }
  return false;
}


const JWT = createJwt({id: 'tmpId', name: 'guille'}, 'this-is-my-private-credential');

console.log(JWT);
console.log(checkJwt(JWT, 'this-is-my-private-credential'));