Don’t use functions as callbacks unless they’re designed for it

Solid advice by Jake:

Here’s an old pattern that seems to be making a comeback:

import { toReadableNumber } from 'some-library';
const readableNumbers = someNumbers.map(toReadableNumber);

Here’s the problem:

// We think of:
const readableNumbers = someNumbers.map(toReadableNumber);
// …as being like:
const readableNumbers = someNumbers.map((n) => toReadableNumber(n));
// …but it's more like:
const readableNumbers = someNumbers.map((item, index, arr) =>
  toReadableNumber(item, index, arr),
);

You might have encountered this yourself when combining map with parseInt, as its second parameter defines the base to use 😅

Don’t use functions as callbacks unless they’re designed for it →