log.js

A dead-simple, lightweight (>8KB) logging utility for Node.js applications in a JSON format.

Installation

log.js is available on the npm registry, and can be installed with a single command:

npm i @jlcarveth/log.js --save

Otherwise, log.js consists of a single javascript file, so it can be downloaded and added to your project manually:

curl https://raw.githubusercontent.com/JLCarveth/log.js/master/log.js > log.js

Usage

The goal of log.js is to be dead simple to use. Simplest use of log.js simply involves replacing console.log calls with Logger.log calls:

import logger from 'log.js'; // Import the package

const Logger = new logger(); // Initialize the package

[...]
Logger.log('A request was made to /api/some/route.');

This will return a nice JSON-formatted string to be output to STDOUT:

{"timestamp":"2022-06-14T15:43:24.516Z","level":"info","message":"A request was made to /api/some/route.","hostname":"JohnC-pc"}

When a log level is not specified, info is used. To specify a log level, do the following:

Logger.log("This is a warning, peace and love.", Logger.LEVELS.WARNING);

The following log levels are available by default:

• info
• warning
• error
• fatal

Additional parameters can be logged easily. Simply store the parameters in an Object and pass it to log():

let data = {
    "headers" : { ... },
    "request" : { ... }
}
Logger.log("Incoming Request on /api/books", data);

Any parameters passed to log() are included in the log messages:

{"timestamp":"2022-06-14T15:31:37.273Z","level":"info","message":"Incoming request","hostname":"JohnC-pc","clientAddress":"::1","targetURL":"https://www.uuidtools.com/api/generate/v5/namespace/ns:url/name/JohnLCarveth","method":"GET","body":{},"headers":{"target-url":"https://www.uuidtools.com/api/generate/v5/namespace/ns:url/name/JohnLCarveth","user-agent":"PostmanRuntime/7.29.0","accept":"*/*","postman-token":"6f92736e-ec2c-4971-9dfe-070c6e448592","host":"localhost:3069","accept-encoding":"gzip, deflate, br","connection":"keep-alive"}}

Command-Line Interface

log.js also provides a command-line tool to allow for JSON logging in other environments, specifically shell scripts. Simply install the package globally:

npm i -g @jlcarveth/log.js

Once installed, the logger binary becomes available. Usage is quite familiar to the Javascript API:

# Basic Usage
$ logger "This is a log message"
{"timestamp":"2022-06-27T12:45:51.716Z","level":"info","message":"This is a log message"}

# Specify log level with -l OR --level
$ logger "This is a test message" -l warning
{"timestamp":"2022-06-27T12:39:06.999Z","level":"warning","message":"This is a test message"}

# Additional data is passed through with a key=value pattern:
$ logger "This is a test message" -l warning x=42 y=21
{"timestamp":"2022-06-27T12:39:15.204Z","level":"warning","message":"This is a test message","x":"42","y":"21"}

Output is JSON-formatted and can be piped to a file or another utility.