isotropic-logger-pretty

Human-readable pretty-printer for isotropic-logger. It turns the logger's JSON records into formatted, colorized console output with timestamps, colored log levels, and structured data, ideal for command-line tools and local development.

This package was previously published as bunyan-stream-isotropic. It has been rebuilt for the pino-based isotropic-logger and renamed; bunyan-stream-isotropic is deprecated.

Why Use This?

• One-Call Setup: A single assignment switches the shared logger to human-readable output.
• Readable Logs: Transforms JSON records into formatted console output that's easy to scan.
• Colored Output: Color-codes log levels using Node's built-in util.styleText, no third-party color dependency.
• Timestamp Formatting: Displays timestamps in a friendly YYYY-MM-DD hh:mm:ss.SSS A format using the Temporal API.
• Structured Data: Renders additional data fields with isotropic-value-to-source.
• Error Details: Special handling for error objects, including stack traces.
• No Truncation: Built on isotropic-console so deep objects and long stacks are printed in full.

Installation

npm install isotropic-logger-pretty

Usage

The simplest way to use this package is to assign outputStream once, typically at the entry point of a command-line tool. Because isotropic-logger is a shared singleton, this affects every module that logs through it:

import _logger from 'isotropic-logger';
import _LoggerPretty from 'isotropic-logger-pretty';

_logger.outputStream = _LoggerPretty();

// Basic logging
_logger.info('Application started');

// Logging with additional data
_logger.info({
    action: 'login',
    status: 'success',
    user: 'john'
}, 'User logged in');

// Logging errors
import _Error from 'isotropic-error';

try {
    throw _Error({
        message: 'Something went wrong'
    });
} catch (error) {
    _logger.error({
        error
    }, 'Operation failed');
}

Output Format

The formatter produces log entries with the following shape:

[YYYY-MM-DD hh:mm:ss.SSS A] LEVEL: Message {additional data}

For example:

[2026-06-15 02:37:42.123 PM] INFO: User logged in {
    action: 'login',
    status: 'success',
    user: 'john'
}

Errors also display their stack traces on the following lines:

[2026-06-15 02:38:15.456 PM] ERROR: Operation failed {
    error: {
        message: 'Something went wrong'
    }
}
Error: Something went wrong
    at Object.<anonymous> (/app/example.js:10:11)
    ...

Log Level Colors

Each log level is displayed with a different color for better visibility:

• TRACE: White
• DEBUG: Yellow
• INFO: Cyan
• WARN: Magenta
• ERROR: Red
• FATAL: Inverse (reversed foreground and background)

Custom (unrecognized) log levels are displayed in bold as LVL <number>.

Data Field Serialization

Additional data fields are formatted with isotropic-value-to-source for consistent, readable output:

_logger.info({
    request: {
        duration: 123,
        method: 'POST',
        path: '/api/users'
    },
    response: {
        status: 201
    }
}, 'API request processed');

Output:

[2026-06-15 02:40:23.789 PM] INFO: API request processed {
    request: {
        duration: 123,
        method: 'POST',
        path: '/api/users'
    },
    response: {
        status: 201
    }
}

Migrating from bunyan-stream-isotropic

This package replaces bunyan-stream-isotropic. The visible output is the same, but it is wired up differently because isotropic-logger is now based on pino rather than Bunyan:

• Enable with one assignment. Instead of clearing logger.streams and calling logger.addStream({ type: 'raw', stream }), assign to _logger.outputStream.
• No color dependency. Coloring now uses Node's built-in util.styleText instead of chalk.
• Temporal timestamps. Timestamps are derived with the Temporal API instead of moment-timezone, with the same YYYY-MM-DD hh:mm:ss.SSS A format.

Contributing

Please refer to CONTRIBUTING.md for contribution guidelines.

Issues

If you encounter any issues, please file them at https://github.com/ibi-group/isotropic-logger-pretty/issues