eslint-plugin-sentence-case

ESLint plugin to enforce sentence case in string literals. Ideal for i18n/locale files, UI text, and any project where consistent text casing matters.

What it does

• Flags strings that don't start with an uppercase letter
• Detects title case ("Show More Items" → "Show more items")
• Auto-fixes violations
• Smart exceptions: acronyms (CSV, URLs, IDs), punctuation, parentheses, allowed words

Installation

npm install -D eslint-plugin-sentence-case

Usage

Flat config (ESLint 9+)

import sentenceCase from 'eslint-plugin-sentence-case';

export default [
  {
    files: ['src/i18n/locales/*.ts'],
    plugins: {
      'sentence-case': sentenceCase,
    },
    rules: {
      'sentence-case/enforce': 'error',
    },
  },
];

With options

'sentence-case/enforce': ['error', {
  // Disable title case detection (only check first letter)
  titleCaseDetection: true,

  // Words that are always allowed to be capitalized
  allowedWords: ['GitHub', 'Obsidian', 'TypeScript'],

  // File path patterns to ignore (regex)
  ignorePaths: ['__tests__', '__mocks__'],
}]

Options

| Option | Type | Default | Description | |--------|------|---------|-------------| | titleCaseDetection | boolean | true | Flag words that are capitalized mid-sentence | | allowedWords | string[] | [] | Words always allowed to be capitalized (brand names, proper nouns) | | ignorePaths | string[] | [] | Regex patterns for file paths to skip |

Smart exceptions

The rule automatically allows capitalization in these cases:

• Acronyms — all-caps words like CSV, URL, AND, OR
• Acronyms with suffixes — URLs, IDs, APIs
• After punctuation — Done. Next step (capital after ., !, ?, :)
• Inside parentheses — Click here (See More)
• Single characters — Column A (single letters are skipped)

Examples

Caught by the rule

// ❌ Lowercase first letter
label: "show more items"     // → "Show more items"

// ❌ Title case
label: "Show More Items"     // → "Show more items"

// ❌ Mixed
label: "export All Data"     // → "Export all data"

Passes the rule

// ✅ Sentence case
label: "Show more items"

// ✅ Acronyms
label: "Export CSV file"
label: "Copy all URLs"

// ✅ After punctuation
label: "Done. Click here"

// ✅ Parentheses
label: "Learn more (See Docs)"

// ✅ Allowed words
label: "Open in GitHub"       // with allowedWords: ["GitHub"]

License

MIT