simple signature with node-crypto api

signature.js

const crypto = require('crypto')

const sign = (value, secret) => {
  return value + '.' + crypto
    .createHmac('sha256', secret + '')
    .update(value + '')
    .digest('base64')
    .replace(/\=+$/, '')
}

const unsign = (value, secret) => {
  value = value + ''
  const str = value.slice(0, value.lastIndexOf('.'))
  const macBuffer = Buffer.from(sign(str, secret + ''))
  const valBuffer = Buffer.alloc(macBuffer.length)
  valBuffer.write(value)
  return crypto.timingSafeEqual(macBuffer, valBuffer) ? str : false
}

// example
const value = 'great'
const secret = 'fuck'
console.log('signed:', sign(value, secret))
console.log('unsigned check:', unsign(sign(value, secret), secret) === value)