Move Statements into Function

Removes smells

Symptom

The same setup (logging, validation, metric tick) or follow-up code appears around every call to a function — repeated boilerplate at every call site.

Goal

Setup or follow-up that happens around every call to a function moves inside the function, so the caller's contract shrinks.

Before the refactoring

log('start fetch');
const data  = fetch(url);
log('start fetch');
const data2 = fetch(url2);

After the refactoring

function fetchLogged(url) {
  log('start fetch');
  return fetch(url);
}

Example source: Illustrative example written for this site, not a quotation from any source.

Pressure

Every caller must remember the boilerplate; missing it produces inconsistent behavior the function doesn't enforce; updates to the boilerplate touch every caller.

Tradeoff

If the moved statements aren't always wanted, the function grows a flag argument — verify every caller really needs the moved behavior.

Relief

One fewer thing to remember at the call site; consistency is enforced by the function's definition, not by convention.

Trap

Moving statements into a function that some callers don't actually want — the function grows a flag argument to make the moved behavior conditional, which is a worse smell.