Replace magic values with named constants and enums

A magic value is any literal — number or string — embedded in logic without a name. They're maintenance traps: when the value changes, you have to find every occurrence by searching for the literal, and you can never be sure you found them all.

// Bad — three magic values
if (retries > 3) throw new Error();
if (order.status === 'pending') processOrder();
if (user.role === 'admin') showDashboard();

Replace them with named constants:

const MAX_RETRY_ATTEMPTS = 3;

const ORDER_STATUS = Object.freeze({
  PENDING: 'pending',
  APPROVED: 'approved',
  REJECTED: 'rejected'
});

const USER_ROLE = Object.freeze({
  ADMIN: 'admin',
  MEMBER: 'member',
  GUEST: 'guest'
});

// Now readable and refactor-safe
if (retries > MAX_RETRY_ATTEMPTS) throw new Error();
if (order.status === ORDER_STATUS.PENDING) processOrder();
if (user.role === USER_ROLE.ADMIN) showDashboard();

Object.freeze() in JavaScript makes the object immutable so values can't be accidentally changed. In TypeScript, use string literal union types or enums for compile-time safety. In Python, use the Enum class.

from enum import Enum

class OrderStatus(Enum):
    PENDING = 'pending'
    APPROVED = 'approved'
    REJECTED = 'rejected'

if order.status == OrderStatus.PENDING: ...

The benefit: if 'pending' ever changes to 'awaiting_payment', you change one constant definition and everything using it updates automatically.