Example of calculating hmac in node.js

calculateHmac.js

import * as crypto from 'crypto'

const merchantSecret = 'secret'
const hash = 'sha256'
const encoding = 'base64'
const payload = {
  id: 123,
  somethingElse: 'not 123'
}

const hmac = crypto
  .createHmac(hash, merchantSecret)
  .update(Buffer.from(JSON.stringify(payload)).toString(encoding))
  .digest('hex')
  .toUpperCase()