Functions should do one thing

☑️ Topic: Functions

☑️ Idea: Create a function for each action or concept. Functions should do one and only one thing.

☑️ Benefits: Readability, reusability, testability, refactorability.

☑️ Guideline: In the function description you shouldn’t need to use “and”, “or” or “if”.


// BAD
function emailClients(clients) {
  clients.forEach(client => {
    const clientRecord = database.lookup(client);
    if (clientRecord.isActive()) {
      email(client);
    }
  });
}


// GOOD
function emailActiveClients(clients) {
  clients.filter(isActiveClient).forEach(email);
}
function isActiveClient(client) {
  const clientRecord = database.lookup(client);
  return clientRecord.isActive();
}