# @thi.ng/logger > Basis types for arbitrary & hierarchical logging Latest version **3.3.11** (published 2026-08-25) · Apache-2.0 license · 0 weekly downloads ## Install ```sh npm install @thi.ng/logger pnpm add @thi.ng/logger yarn add @thi.ng/logger bun add @thi.ng/logger ``` ## Health **Score 70/100 (B)** — status: active. Positive: has types; esm support; no vulnerabilities; recently updated; high maintenance score; high quality score. Warnings: low downloads. ## Facts | | | |---|---| | Version | 3.3.11 | | Published | 2026-08-25 | | First published | 2021-10-12 | | Weekly downloads | 0 | | License | Apache-2.0 | | TypeScript types | bundled | | Module format | ESM | | Node | >=18 | | Dependencies | 0 | | Unpacked size | 33.1 KB | | Known vulnerabilities | 0 | | Install scripts | no | | Author | Karsten Schmidt | | Maintainers | thi.ng | | Keywords | console, filter, hierarchy, logger, memory, typescript | ## Links - npm: https://www.npmjs.com/package/@thi.ng/logger - Repository: https://codeberg.org/thi.ng/umbrella - Homepage: https://thi.ng/logger - Funding: https://github.com/sponsors/postspectacular - npm.io page: https://npm.io/package/@thi.ng/logger ## Alternatives - [cli-color](https://npm.io/package/cli-color.md) — 3.4M weekly downloads - [log](https://npm.io/package/log.md) — 1.3M weekly downloads - [logstash-client](https://npm.io/package/logstash-client.md) — 4.5K weekly downloads - [@nocobase/plugin-logger](https://npm.io/package/@nocobase/plugin-logger.md) — 2.0K weekly downloads - [child-process-debug](https://npm.io/package/child-process-debug.md) — 695 weekly downloads ## Recent versions - 3.3.11 (latest) — 2026-08-25 - 3.3.10 — 2026-07-02 - 3.3.9 — 2026-06-05 - 3.3.8 — 2026-05-23 - 3.3.7 — 2026-05-20 - 3.3.5 — 2026-05-11 - 3.3.4 — 2026-05-08 - 3.3.3 — 2026-04-26 - 3.3.2 — 2026-04-18 - 3.3.1 — 2026-04-02 - 3.3.0 — 2026-03-11 - 3.2.15 — 2026-03-07 - 3.2.14 — 2026-03-07 - 3.2.13 — 2026-02-07 - 3.2.12 — 2026-01-23 - … 117 more at https://npm.io/package/@thi.ng/logger/versions ## README # ![@thi.ng/logger](https://codeberg.org/thi.ng/umbrella/media/branch/develop/assets/banners/thing-logger.svg?7a6ea9dc) [![npm version](https://img.shields.io/npm/v/@thi.ng/logger.svg)](https://www.npmjs.com/package/@thi.ng/logger) ![npm downloads](https://img.shields.io/npm/dm/@thi.ng/logger.svg) [![Mastodon Follow](https://img.shields.io/mastodon/follow/109331703950160316?domain=https%3A%2F%2Fmastodon.thi.ng&style=social)](https://mastodon.thi.ng/@toxi) > [!NOTE] > This is one of 217 standalone projects. LLM-free, human-made and > cared for software, maintained as part of the > [@thi.ng/umbrella](https://codeberg.org/thi.ng/umbrella/) ecosystem and > anti-framework. > > 🚀 Please help me to work full-time on these projects by [sponsoring > me](https://codeberg.org/thi.ng/umbrella/src/branch/develop/CONTRIBUTING.md#donations). > Thank you! ❤️ - [About](#about) - [Log levels](#log-levels) - [Logging hierarchies](#logging-hierarchies) - [Supplied implementations](#supplied-implementations) - [Lazy evaluation](#lazy-evaluation) - [Status](#status) - [Related packages](#related-packages) - [Installation](#installation) - [Dependencies](#dependencies) - [Usage examples](#usage-examples) - [API](#api) - [Authors](#authors) - [License](#license) ## About Basis types for arbitrary & hierarchical logging. The types & implementations provided by this package are used in various places throughout the thi.ng/umbrella ecosystem and can be swapped out on demand to customize users' needs. ### Log levels All loggers based on this basic framework provided by this package support the following [`LogLevel`](https://docs.thi.ng/umbrella/logger/enums/LogLevel.html)s (in order of importance): - `FINE` - `DEBUG` - `INFO` - `WARN` - `SEVERE` Logging calls targeting lower levels than configured in the logger will be ignored. ### Logging hierarchies Each [`ILogger`](https://docs.thi.ng/umbrella/logger/interfaces/ILogger.html) instance (i.e. all supplied here) can have an associated parent logger to which any non-filtered messages can be propagated. This allows for the easy creation of logging hierarchies with each logger able to control its own log level. To that end the package also provides a `ROOT` logger. ```ts import { ConsoleLogger, ROOT } from "@thi.ng/logger"; // create a child logger const myLogger = ROOT.childLogger("custom"); // use console output for root logger (and for all its children) ROOT.set(new ConsoleLogger()); // forwards message to root and then writes to console myLogger.debug("hello"); // [DEBUG] custom: hello ``` ### Supplied implementations The following logger implementations are provided: - [`ConsoleLogger`](https://docs.thi.ng/umbrella/logger/classes/ConsoleLogger.html): writes output to `console` - [`MemoryLogger`](https://docs.thi.ng/umbrella/logger/classes/MemoryLogger.html): writes output to in-memory journal - [`ProxyLogger`](https://docs.thi.ng/umbrella/logger/classes/ProxyLogger.html): proxy impl for another logger - [`StreamLogger`](https://docs.thi.ng/umbrella/logger/classes/StreamLogger.html): writes output to NodeJS stream - [`NULL_LOGGER`](https://docs.thi.ng/umbrella/logger/variables/NULL_LOGGER.html): no-op logger, suppresses all output ### Lazy evaluation Log messages can contain any number & types of arguments. No-arg functions can be provided as message arg to avoid evaluation of potentially costly message formatting for suppressed log levels. For example: ```ts import { ConsoleLogger, LogLevel } from "@thi.ng/logger"; const logger = new ConsoleLogger("app", LogLevel.INFO); const name = "thi.ng"; // eager (standard) arg evaluation logger.info(`hello, ${name}`); // [INFO] app: hello, thi.ng // eager (standard) arg evaluation, but suppressed output logger.debug("result is", 23 + 42); // lazy arg evaluation logger.info("result is", () => 23 + 42); // [INFO] app: result is 65 ``` ## Status **STABLE** - used in production [Search or submit any issues for this package](https://codeberg.org/thi.ng/umbrella/issues?q=%5Blogger%5D) ## Related packages - [@thi.ng/rstream-log](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/rstream-log) - Structured, multilevel & hierarchical loggers based on [@thi.ng/rstream](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/rstream) ## Installation ```bash yarn add @thi.ng/logger ``` ESM import: ```ts import * as log from "@thi.ng/logger"; ``` Browser ESM import: ```html ``` [JSDelivr documentation](https://www.jsdelivr.com/) For Node.js REPL: ```js const log = await import("@thi.ng/logger"); ``` Package sizes (brotli'd, pre-treeshake): ESM: 965 bytes ## Dependencies None ## Usage examples One project in this repo's [/examples](https://codeberg.org/thi.ng/umbrella/src/branch/develop/examples) directory is using this package: | Screenshot | Description | Live demo | Source | |:--------------------------------------------------------------------------------------------------------------------------|:-------------------------------------------------------------------------------|:---------------------------------------------------------|:----------------------------------------------------------------------------------------------| | | Declarative component-based system with central rstream-based pubsub event bus | [Demo](https://demo.thi.ng/umbrella/rstream-system-bus/) | [Source](https://codeberg.org/thi.ng/umbrella/src/branch/develop/examples/rstream-system-bus) | ## API [Generated API docs](https://docs.thi.ng/umbrella/logger/) TODO ## Authors - [Karsten Schmidt](https://thi.ng) If this project contributes to an academic publication, please cite it as: ```bibtex @misc{thing-logger, title = "@thi.ng/logger", author = "Karsten Schmidt", note = "https://thi.ng/logger", year = 2016 } ``` ## License © 2016 - 2026 Karsten Schmidt // Apache License 2.0 --- _Source: https://npm.io/package/@thi.ng/logger · Machine-readable twin of the npm.io package page. 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