prefer-logger

Category: Suggestion
Fixable: No (suggestions only for log-only mode)

What it does

Discourages the use of console.log (and optionally all console methods) in favor of intentional logging habits or a dedicated logger library.

The rule has two modes:

• log-only (default) — Only console.log is flagged. It is treated like a debugger statement: a tool for quick debugging that should not appear in committed code. A suggestion is provided to replace it with console.info for output that is genuinely intentional.
• all — Every console.* call is flagged. Use this when your team has adopted a dedicated logger (e.g. pino, winston) and wants to eliminate all direct console usage.

Why

console.log is the most common debugging leftover in codebases. It is easy to add during development and easy to forget before committing. When teams rely on logs for production observability, console.log is noisy and unstructured compared to a proper logger.

At the same time, console.info, console.warn, and console.error carry semantic meaning — they signal intent. Restricting only console.log lets teams keep meaningful console output while eliminating accidental debug noise.

For teams that go further and adopt structured logging (pino, winston, etc.), restricting all console.* calls enforces consistency and ensures every log statement goes through the configured logger.

Examples

log-only mode (default)

❌ Invalid

console.log('user id:', userId); // debug leftover
console.log(response);

✅ Valid

console.info('server started on port 3000'); // intentional
console.warn('rate limit approaching');
console.error('unhandled exception', err);
logger.info({ userId }, 'user logged in'); // dedicated logger

all mode

❌ Invalid

console.log('debug');
console.info('server started'); // must use dedicated logger
console.warn('deprecated');
console.error('error', err);

✅ Valid

logger.info('server started');
logger.warn('deprecated API called');
logger.error({ err }, 'unhandled exception');

Suggestion

In log-only mode, the rule provides a one-click suggestion to replace console.log with console.info:

// Before (reported)
console.log('request received');

// After (applying suggestion)
console.info('request received');

Options

interface PreferLoggerOptions {
  /**
   * Which console calls to restrict.
   * - 'log-only' — only console.log (default)
   * - 'all'      — all console.* methods
   */
  mode?: 'log-only' | 'all';
}

Option	Type	Default	Description
mode	'log-only' | 'all'	'log-only'	Controls which console calls are flagged

Configuration

Flat config (ESLint v9+)

// eslint.config.mjs
import lintlord from 'eslint-plugin-lintlord';

export default [
  {
    plugins: { lintlord },
    rules: {
      // Default: restrict only console.log
      'lintlord/prefer-logger': 'warn',

      // Strict: restrict all console methods
      'lintlord/prefer-logger': ['error', { mode: 'all' }],
    },
  },
];

Legacy .eslintrc

{
  "plugins": ["lintlord"],
  "rules": {
    "lintlord/prefer-logger": "warn",
    "lintlord/prefer-logger": ["error", { "mode": "all" }]
  }
}

Built-in configs

Config	Severity	Options
recommended	error	mode: 'log-only'
strict	error	mode: 'all'