explicit-code.js

// Good

let { parameters, customParameters } = connection;

let firstName = customParameters.get("FirstName");
let lastName = customParameters.get("LastName");

// Lets say we now need to pass eventId.
// One could easily add it inside caller as it
// already has multiple props, and things are a bit
// implicit.
send({
  type: "INCOMING",
  caller: {
    name:
      firstName && lastName
        ? `${lastName}, ${firstName}`
        : firstName || lastName || null,
    email: customParameters.get("From")
  }
});

// Better

let { parameters, customParameters } = connection;

function createCaller() {
  let firstName = customParameters.get("FirstName");
  let lastName = customParameters.get("LastName");
  let email = customParameters.get("From");

  let name =
    firstName && lastName
      ? `${lastName}, ${firstName}`
      : firstName || lastName || null;

  return { name, email };
}

// As we are explicitly calling createCaller(),
// it's easy to understand that eventId shouldn't be part
// of createCaller().
send({ type: "INCOMING", caller: createCaller() });

// Notes

// Of course this problem could be easily catched
// by some typing system, but what I want is to
// make code easier to read. I prefer to reduce bugs
// by writing explicit code, which may result in more lines,
// instead of introducing a potential bug, so then another
// tool might catch it.