Express Request/Response Logger Middleware

Common errors

• TypeError: expressLogging is not a function

  cause This error typically occurs when attempting to use the `expressLogging` function directly without passing a logger instance, or if importing it incorrectly in an ESM environment.
  fix Ensure you are calling `expressLogging` with a logger argument (e.g., `app.use(expressLogging(logger));`) and that you are using `const expressLogging = require('express-logging');` in a CommonJS context.

• TypeError: logger.info is not a function

  cause The `express-logging` middleware expects the provided logger object to have an `info` method that accepts string formatting or a params object.
  fix Verify that the logger object you are passing to `expressLogging` (e.g., `logger`) has a callable `info` method with the expected signature. For instance, `logops` provides this by default.

Warnings

• breaking This package is no longer maintained and has not been updated in over eight years. It is highly likely to be incompatible with modern versions of Node.js (e.g., Node.js 14+) and Express (e.g., Express 5). Using it may lead to unexpected errors or security vulnerabilities.
  Fix: Consider using a modern, actively maintained logging middleware for Express such as `morgan`, `pino-http`, or `winston-express`.
• gotcha The package explicitly targets older Node.js versions (engines: `>= 0.10.26`). It was last updated to fix compatibility with 'old node releases,' implying it was not designed with current Node.js features or performance characteristics in mind.
  Fix: Migration to a contemporary logging solution is strongly recommended to ensure compatibility and leverage modern Node.js features.
• gotcha The middleware is CommonJS-only. Attempting to use `import expressLogging from 'express-logging';` in an ES module context will fail with a `TypeError: expressLogging is not a function` or a similar module resolution error.
  Fix: Ensure your project is configured for CommonJS (`"type": "commonjs"` in package.json) or stick to `require()` syntax for this specific package. For ES module projects, choose an alternative middleware.

Install

• npm install express-logging npm
• yarn add express-logging yarn
• pnpm add express-logging pnpm

Imports

• expressLogging
  wrong:

  import expressLogging from 'express-logging';

  correct:

  const expressLogging = require('express-logging');

  This package is CommonJS-only and does not support ES modules. Attempting to import it with `import` will result in a syntax error or a default import object.
• logger
  wrong:

  import logger from 'logops';

  correct:

  const logger = require('logops'); // Or your preferred logger

  The logger passed to expressLogging must be a CommonJS module. Ensure your chosen logger exposes an `.info` method.
• app.use
  wrong:

  app.use(expressLogging); // Missing logger argument

  correct:

  app.use(expressLogging(logger, options));

  The middleware factory function `expressLogging` must be called with a logger instance as its first argument.

Quickstart

Demonstrates basic usage of `express-logging` with a standard logger and an example of configuring the middleware with custom blacklist paths and a 'params' logging policy.

const express = require('express');
const expressLogging = require('express-logging');
const logger = require('logops'); // Example logger

const app = express();

// Basic usage: Log all requests/responses
app.use(expressLogging(logger));

// Example route
app.get('/', (req, res) => {
  res.send('Hello, World!');
});

// Example with custom options: blacklist '/images' and use 'params' policy
const blacklistPaths = ['/images', '/html'];
app.use('/api', expressLogging(logger, { blacklist: blacklistPaths, policy: 'params' }));

app.get('/images/test.png', (req, res) => {
  res.send('This image access should not be logged by the second middleware.');
});

app.get('/api/data', (req, res) => {
  res.json({ message: 'API data' });
});

const PORT = process.env.PORT ?? 3000;
app.listen(PORT, () => {
  console.log(`Server listening on port ${PORT}`);
});