luminous

Highly configurable logger for Deno with multiple transports and formatters.

Note: This package is under active development. Contributions, feedback, and pull requests are welcome!

Contents

• Quick Start
• Installation
• Logging Levels
• Creating Loggers
• Transports
• Formatters
• Examples
• API Reference
• License

Quick Start

import luminous from "jsr:@vseplet/luminous";

// Create a logger with name
const log = new luminous.Logger("MyApp");
log.inf`Hello, World!`;
// 02:15:30.123 [INF] MyApp: Hello, World!

Installation

deno add @vseplet/luminous

import luminous from "@vseplet/luminous";

Logging Levels

Luminous provides 8 logging levels:

Level	Method	Short Name	Description
0	trc()	TRC	Most detailed information for debugging
1	dbg()	DBG	Debug information during development
2	vrb()	VRB	Verbose information about application state
3	inf()	INF	General information about application operation
4	usr()	USR	User-related events and actions
5	wrn()	WRN	Warnings about potential issues
6	err()	ERR	Errors that occur but are recoverable
7	ftl()	FTL	Critical errors that may stop the application

const log = new luminous.Logger("MyApp");

log.trc`Trace message`; // [TRC]
log.dbg`Debug message`; // [DBG]
log.vrb`Verbose message`; // [VRB]
log.inf`Info message`; // [INF]
log.usr`User message`; // [USR]
log.wrn`Warning message`; // [WRN]
log.err`Error message`; // [ERR]
log.ftl`Fatal message`; // [FTL]

Creating Loggers

Basic Logger

// Create a named logger
const log = new luminous.Logger("MyApp");

// Create default logger
const log = new luminous.Logger(); // name: "default"

// Create with options
const log = new luminous.Logger({
  name: "MyApp",
  level: luminous.Level.INFO,
  formatter: new luminous.formatters.TextFormatter(),
  transport: new luminous.transports.TerminalTransport(),
});

Hierarchical Loggers

Create child loggers that inherit configuration from parent:

// Create parent logger
const parent = new luminous.Logger({
  name: "App",
  formatter: new luminous.formatters.TextFormatter({
    showMetadata: true,
    timestampPattern: "yyyy-MM-dd HH:mm:ss",
  }),
  transport: new luminous.transports.TerminalTransport(),
});

// Create child loggers
const apiLog = parent.child("API");
const dbLog = parent.child("Database", "db"); // with postfix

apiLog.inf`Request received`; // [INF] App.API: Request received
dbLog.wrn`Connection slow`; // [WRN] App.Database db: Connection slow

// Deep hierarchy with postfix
const userLog = apiLog.child("User", "auth"); // postfix as string
userLog.dbg`User authenticated`; // [DBG] App.API.User auth: User authenticated

// Child with custom options
const customChild = parent.child("Custom", {
  postfix: "test",
  level: luminous.Level.WARN,
});

Transports

Transports send formatted log messages to their destination. Default transport is TerminalTransport (automatically applied).

import { TerminalTransport } from "jsr:@vseplet/luminous/transports";

// Custom transport
const log = new luminous.Logger({
  name: "MyApp",
  formatter: new luminous.formatters.TextFormatter(),
  transport: new TerminalTransport(),
});

Formatters

Formatters convert log data into strings. Available formatters:

TextFormatter

Human-readable text format with colors:

import { TextFormatter } from "jsr:@vseplet/luminous/formatters";

const formatter = new TextFormatter({
  showMetadata: true,
  showTimestamp: true,
  timestampPattern: "yyyy-MM-dd HH:mm:ss",
  colorize: true,
});

JsonFormatter

JSON format for structured logging:

import { JsonFormatter } from "jsr:@vseplet/luminous/formatters";

const formatter = new JsonFormatter({
  timestampPattern: "yyyy-MM-dd HH:mm:ss",
});

Examples

Basic Usage

import luminous from "@vseplet/luminous";

const log = new luminous.Logger("MyApp");
log.inf`Application started`;
log.err(new Error("Something went wrong"));
// Metadata is passed as second argument (doesn't work with template strings)
log.inf("User logged in", { userId: 123, username: "john" });

Hierarchical Logging

import luminous from "@vseplet/luminous";

// Setup parent logger
const app = new luminous.Logger("App");

// Create module loggers
const api = app.child("API");
const db = app.child("Database");

api.inf`Server started on port 3000`;
db.wrn`Connection pool exhausted`;

Custom Configuration

import luminous from "@vseplet/luminous";

const log = new luminous.Logger({
  name: "MyApp",
  level: luminous.Level.INFO,
  formatter: new luminous.formatters.TextFormatter({
    showMetadata: true,
    timestampPattern: "HH:mm:ss",
  }),
  transport: new luminous.transports.TerminalTransport(),
});
log.inf`Custom configured logger`;

Run examples:

deno task example:simple      # Basic usage
deno task example:hierarchy   # Hierarchical loggers

API Reference

Logger

• new Logger(name?) - Create logger with name (string) or options (object)
• new Logger(options?) - Create logger with options object
• logger.child(name, options?) - Create child logger (options can be object or postfix string)
• logger.trc(msg, metadata?) - Log trace message
• logger.dbg(msg, metadata?) - Log debug message
• logger.vrb(msg, metadata?) - Log verbose message
• logger.inf(msg, metadata?) - Log info message
• logger.usr(msg, metadata?) - Log user message
• logger.wrn(msg, metadata?) - Log warning message
• logger.err(msg | Error, metadata?) - Log error message
• logger.ftl(msg, metadata?) - Log fatal message

License

MIT