How to use the chloride.crypto_secretbox_open_easy function in chloride

function unbox (ctxt, key) {
  var b = Buffer.from(ctxt, 'base64')
  var ptxt = chloride.crypto_secretbox_open_easy(b, key.slice(0, 24), key)
  if(!ptxt) return
  try {
    return JSON.parse(ptxt)
  } catch(err) {
    console.error(err)
  }
}

function unbox_detached (mac, boxed, nonce, key) {
  return sodium.crypto_secretbox_open_easy(concat([mac, boxed]), nonce, key)
}

exports.secretUnbox = function secretUnbox (ctxt, key) {
  var ptxt = sodium.crypto_secretbox_open_easy(ctxt, key.slice(0, 24), key)
  if(!ptxt) return
  return JSON.parse(ptxt.toString())
}