#  [](https://www.npmjs.com/package/@thi.ng/rstream-log)  [](https://mastodon.thi.ng/@toxi) > [!NOTE] > This is one of 214 standalone projects, 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) - [Status](#status) - [Support packages](#support-packages) - [Related packages](#related-packages) - [Installation](#installation) - [Dependencies](#dependencies) - [API](#api) - [Authors](#authors) - [License](#license) ## About Structured, multilevel & hierarchical loggers based on [@thi.ng/rstream](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/rstream). This package provides extensible, multi-level & multi-hierarchy logging infrastructure, with logged values transformable via [@thi.ng/transducers](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/transducers). Several built-in transformers are provided. The `Logger` class in this package implements the [@thi.ng/logger](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/logger) `ILogger` interface and uses `LogLevel` enums to configure levels / filtering. See that package for more details. ## Status **STABLE** - used in production [Search or submit any issues for this package](https://codeberg.org/thi.ng/umbrella/issues?q=%5Brstream-log%5D) ## Support packages - [@thi.ng/rstream-log-file](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/rstream-log-file) - File output handler for structured, multilevel & hierarchical loggers based on [@thi.ng/rstream](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/rstream) ## Related packages - [@thi.ng/logger](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/logger) - Basis types for arbitrary & hierarchical logging ## Installation ```bash yarn add @thi.ng/rstream-log ``` ESM import: ```ts import * as rslog from "@thi.ng/rstream-log"; ``` Browser ESM import: ```html ``` [JSDelivr documentation](https://www.jsdelivr.com/) For Node.js REPL: ```js const rslog = await import("@thi.ng/rstream-log"); ``` Package sizes (brotli'd, pre-treeshake): ESM: 749 bytes ## Dependencies - [@thi.ng/api](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/api) - [@thi.ng/checks](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/checks) - [@thi.ng/logger](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/logger) - [@thi.ng/rstream](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/rstream) - [@thi.ng/strings](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/strings) - [@thi.ng/transducers](https://codeberg.org/thi.ng/umbrella/src/branch/develop/packages/transducers) Note: @thi.ng/api is in _most_ cases a type-only import (not used at runtime) ## API [Generated API docs](https://docs.thi.ng/umbrella/rstream-log/) ```ts tangle:export/readme.ts import { LogLevel } from "@thi.ng/logger"; import { Logger, formatString, writeConsole } from "@thi.ng/rstream-log"; const logger = new Logger("main"); // or with min level const logger = new Logger("main", LogLevel.DEBUG); // or min level given as string const logger = new Logger("main", "DEBUG"); // add console output w/ string formatter (a transducer) // each logger instance has a rstream Stream instance // allowing for downstream processing logger.stream.transform(formatString()).subscribe(writeConsole()); logger.debug("hello world"); // [DEBUG] main: 2024-02-16T20:38:11.143Z hello world logger.warn("eek"); // [WARN] main: 2024-02-16T20:38:11.144Z eek // loggers can form hierarchies by creating/attaching child loggers const child = logger.childLogger("child", LogLevel.INFO); import { postWorker } from "@thi.ng/rstream"; // additionally send messages from this logger to worker child.stream.subscribe(postWorker("log-worker.js")); child.info("hi from submodule"); // [INFO] child: 2024-02-16T20:38:11.145Z hi from submodule ``` ## Authors - [Karsten Schmidt](https://thi.ng) If this project contributes to an academic publication, please cite it as: ```bibtex @misc{thing-rstream-log, title = "@thi.ng/rstream-log", author = "Karsten Schmidt", note = "https://thi.ng/rstream-log", year = 2017 } ``` ## License © 2017 - 2026 Karsten Schmidt // Apache License 2.0