express-dynamic-logger

Minimal middleware for Node.js/Express to provide dynamic, configurable logging with both automatic request/response logs and manual developer logs.

📦 Installation

npm install express-dynamic-logger

Or with Yarn:

yarn add express-dynamic-logger

🚀 Usage

Ensure you register body-parsing middleware before mounting the logger so that req.body is populated correctly:

const express = require('express');
const app = express();

// 1. Register body parsers
app.use(express.json());       // for JSON bodies
app.use(express.urlencoded({ extended: true })); // for URL-encoded bodies

// 2. Mount the dynamic logger

const logger = require('express-dynamic-logger');
app.use(logger()); // default options

To customize the logger, pass options into the factory:

app.use(logger({
  logPrefix: '[APP]',
  printAutoLogs: true,
  printManualLogs: true,
  // ...other options...
}));

Manual Logging

Use req.log in your route handlers to emit custom messages at any level:

app.get('/items', (req, res) => {
  req.log.debug('Fetching items', { filter: req.query });
  req.log.info('Items fetched successfully');
  req.log.warn('Response size is large');
  req.log.error('Failed to process item', { id: 123 });
  req.log.fatal('Critical failure!');
  res.send(items);
});

This demonstrates how to call req.log.debug/info/warn/error/fatal for manual logs.

⚙️ Configuration Options

| Option | Type | Default | Description | |---------------------------|------------|-------------------------------|--------------------------------------------------------------------------------------------------| | level | string | 'info' | Log level for automatic logs ([INI], [END]). | | printAutoLogs | boolean | true | Whether to print automatic logs. | | printManualLogs | boolean | true | Whether to print developer-invoked logs (req.log.*).
| skipPreflight | boolean | false | Whether to skip logging CORS preflight (OPTIONS) requests | | | requestIdHeader | string | 'x-request-id' | Header name used to propagate or generate a request ID. | | autoGenerateRequestId | boolean | true | Generate a UUID request ID if the header is missing. | | skipPaths | string[] | ['/health','/favicon.ico'] | Array of routes to ignore (no logging). | | deepHeaders | boolean | true | Include all headers; if false, filter out common browser headers. | | redact | string[] | ['authorization'] | List of header names to mask with ****. | | logPrefix | string | '' | Global prefix prepended to every log entry. | | statusPrefix100 | string | '' | Prefix for 1xx HTTP status logs. | | statusPrefix200 | string | '' | Prefix for 2xx HTTP status logs. | | statusPrefix300 | string | '' | Prefix for 3xx HTTP status logs. | | statusPrefix400 | string | '' | Prefix for 4xx HTTP status logs. | | statusPrefix500 | string | '' | Prefix for 5xx HTTP status logs. | | levelPrefixDebug | string | '' | Prefix for req.log.debug messages. | | levelPrefixInfo | string | '' | Prefix for req.log.info messages. | | levelPrefixWarn | string | '' | Prefix for req.log.warn messages. | | levelPrefixError | string | '' | Prefix for req.log.error messages. | | levelPrefixFatal | string | '' | Prefix for req.log.fatal messages. |

✨ Examples

Default Behavior

app.use(logger());
app.get('/ping', (req, res) => {
  req.log.info('Ping handler');
  res.send('pong');
});

Disable Auto-Logs

app.use(logger({ printAutoLogs: false }));

Disable Manual Logs

app.use(logger({ printManualLogs: false }));

Skip Paths and Custom Request ID

app.use(logger({
  skipPaths: ['/health'],
  requestIdHeader: 'x-custom-id',
  autoGenerateRequestId: false
}));

Filter and Redact Headers

app.use(logger({
  deepHeaders: false,
  redact: ['authorization', 'cookie']
}));

Custom HTTP Status Prefixes

app.use(logger({
  statusPrefix200: '[OK]',
  statusPrefix400: '[BAD_REQ]',
  statusPrefix500: '[ERR]'
}));

Prefix Configuration Only

app.use(logger({
  logPrefix: '[APP]',
  statusPrefix200: '[SUCCESS]',
  statusPrefix400: '[CLIENT_ERR]',
  statusPrefix500: '[SERVER_ERR]',
  levelPrefixDebug: '🐛',
  levelPrefixInfo: 'ℹ️',
  levelPrefixWarn: '⚠️',
  levelPrefixError: '❌',
  levelPrefixFatal: '💀'
}));

Ignore preflight CORS

app.use(logger({
  skipPreflight: true
}));

🚧 Error Resilience

All logging logic runs inside a single try/catch, so internal errors will be printed via console.error without interrupting the server.

📄 License

This project is open source under the MIT License.