Lighthouse Logger

Common errors

• ERR_REQUIRE_ESM: require() of ES Module .../node_modules/lighthouse-logger/index.js from .../my-app.js not supported

  cause Attempting to import `lighthouse-logger` (an ES Module) using CommonJS `require()` in a context where only ESM is expected or configured.
  fix Change your import statement to use ES Modules: `import { Logger } from 'lighthouse-logger';`. If in Node.js, ensure your `package.json` has `"type": "module"` or use `.mjs` file extensions for your module.

• TypeError: Logger is not a constructor

  cause The `Logger` class might not be correctly imported or accessed, often due to incorrect import syntax for named exports.
  fix Ensure you are using named imports for `Logger`: `import { Logger } from 'lighthouse-logger';`. Avoid `import Logger from 'lighthouse-logger';` as it is not a default export.

Warnings

• gotcha The `lighthouse-logger` package is internally managed within the Lighthouse monorepo and has been described as an 'awkward package to maintain' for external consumption. While currently available on npm, future external support or major updates might be limited, or the Lighthouse project might advise against its direct external use. Consider its 'maintenance' status when integrating into new projects.
  Fix: Review the latest Lighthouse project guidelines for logging if you intend to use it in a related project, or consider a more general-purpose logging library for independent applications.
• breaking Version 2.x of `lighthouse-logger` is primarily distributed as an ES Module (ESM). Attempting to import it using CommonJS `require()` syntax in a Node.js environment configured for ESM or in a browser context might lead to errors.
  Fix: Ensure your project uses ES Module import syntax (`import { Logger } from 'lighthouse-logger';`) and your Node.js environment is configured for ESM (e.g., `"type": "module"` in `package.json` or `.mjs` file extension).

Install

• npm install lighthouse-logger npm
• yarn add lighthouse-logger yarn
• pnpm add lighthouse-logger pnpm

Imports

• Logger
  wrong:

  const Logger = require('lighthouse-logger');

  correct:

  import { Logger } from 'lighthouse-logger';

  The primary export is a Logger class. Version 2.x is designed for ES Modules.
• setLevel
  wrong:

  const { setLevel } = require('lighthouse-logger');

  correct:

  import { setLevel } from 'lighthouse-logger';

  A utility function to control the logging verbosity programmatically. ESM-only.
• *
  wrong:

  import LighthouseLogger from 'lighthouse-logger';

  correct:

  import * as LighthouseLogger from 'lighthouse-logger';

  There is no default export; all utilities are named exports. CommonJS requires the `require()` syntax.

Quickstart

Demonstrates how to import the Logger class, set its logging level, and use various logging methods.

import { Logger, setLevel } from 'lighthouse-logger';

// Set the desired logging level (e.g., 'verbose', 'log', 'info', 'warn', 'error', 'silent')
// By default, it might log based on debug environment variables or a default level.
setLevel('verbose');

const myLogger = new Logger('my-app');

myLogger.log('Starting application...');
myLogger.info('Configuration loaded successfully.');
myLogger.warn('Potential issue: API endpoint might be deprecated.');
myLogger.error('Critical error: Failed to connect to database!');

// Example of more detailed logging with specific log IDs
myLogger.log('Processing data for user', { userId: 123, dataSize: '1.5MB' });

// You can also create sub-loggers for different modules
const dataProcessorLogger = new Logger('my-app:data-processor');
dataProcessorLogger.verbose('Entering data processing module.');

// Example of setting level via environment variable for Node.js
// process.env.DEBUG = 'my-app*' // This would enable debug logs for 'my-app' namespace
console.log('\nCheck your console output for logs. Note: ' + 
            'Actual output depends on environment variables (e.g., DEBUG) and setLevel call.');