Use named exports

Export values and types by name, and avoid default exports except where a framework requires them.

Implementation

• Write export function formatCurrency() and import it as import { formatCurrency } from './format-currency'.
• Allow default exports only where a framework requires them, such as some file-based routing pages or configuration files, through a lint override for those paths.
• Enforce with import/no-default-export.

This is a consistency convention.

Rationale

A named export has one name that every import must use, so searching finds every use, and a rename tool updates them all. A default export can be imported under any name, which scatters different names for the same thing, and a missing default export is not always caught.

Examples

Incorrect (counterexample):

export default function formatCurrency(amount: number): string {
  return amount.toFixed(2);
}

import formatMoney from './format-currency';

Correct:

export function formatCurrency(amount: number): string {
  return amount.toFixed(2);
}

import { formatCurrency } from './format-currency';

Validation

Run the lint rule, and check that its overrides cover only paths where a framework requires default exports.

A default export required by a framework is not a violation.