@firebase/logger

What is @firebase/logger?

The @firebase/logger npm package is a utility library for logging purposes within Firebase applications. It provides a flexible, extensible logging solution that can be easily integrated into any Firebase project. The package allows developers to log messages at different levels (e.g., debug, info, warn, error) and to configure the logging behavior to suit their needs.

What are @firebase/logger's main functionalities?

Configurable log levels

This feature allows developers to set the log level, controlling which types of log messages are actually printed to the console or other outputs. In the code sample, the log level is set to 'debug', which means all levels of logs will be shown.

const { Logger } = require('@firebase/logger');

const logger = new Logger();
logger.logLevel = 'debug';
logger.debug('This is a debug message.');

Custom log handlers

Developers can add custom handlers to process the log messages. In the example, a custom handler is added to specifically handle error messages differently by logging them to the console's error stream.

const { Logger } = require('@firebase/logger');

const logger = new Logger();
logger.addHandler((logLevel, ...args) => {
  if (logLevel === 'error') {
    console.error(...args);
  }
});
logger.error('This is an error message.');

Other packages similar to @firebase/logger

winston

Winston is a popular logging library for Node.js. Similar to @firebase/logger, it supports multiple transport options for logging (e.g., console, file, HTTP). Winston provides more built-in transports and is more configurable than @firebase/logger, making it suitable for more complex logging needs.

bunyan

Bunyan is another Node.js logging library that focuses on JSON logging. Like @firebase/logger, it allows for different log levels and custom streams. However, Bunyan's output is more structured and is designed to be more easily parsed by systems than the more straightforward text logging of @firebase/logger.

README

@firebase/logger

This package serves as the base of all logging in the JS SDK. Any logging that is intended to be visible to Firebase end developers should go through this module.

Basic Usage

Firebase components should import the Logger class and instantiate a new instance by passing a component name (e.g. @firebase/<COMPONENT>) to the constructor.

e.g.

import { Logger } from '@firebase/logger';

const logClient = new Logger(`@firebase/<COMPONENT>`);

Each Logger instance supports 5 log functions each to be used in a specific instance:

• debug: Internal logs; use this to allow developers to send us their debug logs for us to be able to diagnose an issue.
• log: Use to inform your user about things they may need to know.
• info: Use if you have to inform the user about something that they need to take a concrete action on. Once they take that action, the log should go away.
• warn: Use when a product feature may stop functioning correctly; unexpected scenario.
• error: Only use when user App would stop functioning correctly - super rare!

Log Format

Each log will be formatted in the following manner:

`[${new Date()}]  ${COMPONENT_NAME}: ${...args}`