no-magic-strings.md

no-magic-strings

Disallow magic string literals in comparisons and switch-case clauses; use named constants instead.

Rule Details

Property	Value
Type	suggestion
Fixable	No
Recommended	warn
Strict	error

Rationale

String literals used in comparisons (=== 'admin') or switch cases are magic strings: their meaning is implicit, they can be mis-typed silently, and every occurrence must be updated if the value changes. Defining them as named constants (const ROLE_ADMIN = 'admin') adds meaning and creates a single source of truth.

Checked locations:

• ===, !==, ==, != binary comparisons
• switch case test values

typeof comparisons are exempt (for example, typeof value === 'string').

Examples

✅ Correct

const ROLE_ADMIN = 'admin';
const STATUS_ACTIVE = 'active';

if (user.role === ROLE_ADMIN) {
  /* ... */
}

switch (user.status) {
  case STATUS_ACTIVE:
    break;
}

❌ Incorrect

if (user.role === 'admin') {
  /* ... */
}

switch (user.status) {
  case 'active':
    break;
  case 'inactive':
    break;
}

Configuration

This rule accepts an optional options object:

'zero-tolerance/no-magic-strings': [
  'error',
  {
    checkComparisons: true,
    checkSwitchCases: true,
    ignoreValues: ['production'],
  },
]