Skip to main content
Deno 2 is finally here 🎉️
Learn more

🐀 Ratlog library for Deno - Application Logging for Rats, Humans, and Machines

Github release version (semver) GitHub commits since latest release (by SemVer) License

unit test status (Github Actions) code analysis status

On deno.land/x/ as ratlog

Deno implementation of Ratlog log formatter.

Getting started

This package exposes two APIs. The more fully-featured of the two tries to match the Ratlog.js API, and is henceforth called the Classic API.

// Import the Classic API from deno.land/x/
import ratlog from "https://deno.land/x/ratlog/classic-api.ts";

// Set up logging through the console output
const log = ratlog(console.log);

log("hello, world");
//> hello, world

// Add fields
log("counting", { count: 1 });
//> counting | count: 1

// Add fields and a tag
log("counting", { count: -1 }, "negative");
//> [negative] counting | count: -1

// Create another logger bound to a tag
const warn = log.tag("warning");

warn("disk space low");
//> [warning] disk space low

// Combine and nest tags any way you like
const critical = warn.tag("critical");

critical("shutting down all servers");
//> [warning|critical] shutting down all servers

// Parse messages
ratlog.parse("[negative] counting | count: -1");
// returns { message: "counting", tags: ["negative"], fields: { count: -1 } }

ratlog.parse("counting | count: 1");
// returns { message: "counting", fields: { count: 1 } }

The core of the implementation is exposed in ./ratlog.ts, and is called the Core API. There’s less syntactic sugar here.

// Import the Core API from deno.land/x/
import Ratlog from "https://deno.land/x/ratlog/ratlog.ts";

Ratlog.log({ message: "hello, world" });
// returns "hello, world"

Ratlog.log({ message: "counting", fields: { count: 1 } });
// returns "counting | count: 1"

Ratlog.log({ message: "counting", tags: ["negative"], fields: { count: -1 } });
// returns "[negative] counting | count: -1"

Ratlog.parse("[negative] counting | count: -1");
// returns { message: "counting", tags: ["negative"], fields: { count: -1 } }

Ratlog.parse("counting | count: 1");
// returns { message: "counting", fields: { count: 1 } }

Ratlog.parse("hello, world");
// returns { message: "hello, world" }

How to help