#factory-function code explainers

javascript

const ROLE_PERMISSIONS = {
  admin: ['users:read', 'users:write', 'billing:read', 'billing:write'],
  manager: ['users:read', 'billing:read'],
  member: ['users:read'],

Role-based permissions middleware in Express

authorization middleware rbac

Intermediate 9 steps

javascript

function usePagination(items, pageSize = 10) {
  let currentPage = 1;
  const totalPages = Math.max(1, Math.ceil(items.length / pageSize));

A closure-based pagination helper in JS

closures encapsulation factory-function

Intermediate 9 steps

javascript

const formatters = new Map();
 
function getFormatter(locale, currency) {
  const key = `${locale}:${currency}`;

Caching Intl.NumberFormat for currency formatting

memoization internationalization caching

Intermediate 8 steps

javascript

function createCountdownTimer(durationSeconds, { onTick, onComplete } = {}) {
  let remaining = durationSeconds;
  let intervalId = null;

Building a countdown timer with closures

closures factory-function timers

Intermediate 9 steps