no-magic-numbers

Disallow numeric literals whose meaning is not carried by a named constant

Rule Details

if (retries > 3) makes the reader reverse-engineer what 3 means; if (retries > MAX_RETRIES) does not. The rule reports numeric literals used directly in logic and offers a suggestion to extract a named constant.

Structural, allowlisted exceptions keep the rule quiet where a bare number IS the clearest spelling: 0, 1, -1, 2 (indexing, off-by-one arithmetic, parity), and any literal already assigned to a SCREAMING_CASE constant.

Examples

❌ Incorrect

setTimeout(poll, 5000);
if (attempts > 3) giveUp();

✅ Correct

const TIMEOUT_MS = 5000;
const MAX_RETRIES = 3;

setTimeout(poll, TIMEOUT_MS);
if (attempts > MAX_RETRIES) giveUp();

const first = items[0];   // structural allowlist: 0, 1, -1, 2

Configuration Examples

Basic Usage

// eslint.config.js
{
  rules: {
    'conventions/no-magic-numbers': 'warn',
  },
}

When Not To Use It

Test files and fixtures, where literal values are the point. Scope the rule to production source in your config rather than disabling it globally.