• About
  • Log levels
  • Supplied implementations
  • Lazy evaluation
• Status
• Related packages
• Installation
• Dependencies
• Usage examples
• API
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• License

Types & basis infrastructure for arbitrary logging (w/ default impls).

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.

All loggers based on this basic framework provided by this package support the following LogLevels (in order of importance):

• FINE
• DEBUG
• INFO
• WARN
• SEVERE

Logging calls targetting lower levels than configured in the logger will be ignored.

The following logger implementations are provided:

• ConsoleLogger: writes output to console
• MemoryLogger: writes output to in-memory journal
• NULL_LOGGER: no-op logger, suppresses all output

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:

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

STABLE - used in production

Search or submit any issues for this package

• @thi.ng/rstream-log - Structured, multilevel & hierarchical loggers based on @thi.ng/rstream

yarn add @thi.ng/logger

ES module import:

<script type="module" src="https://cdn.skypack.dev/@thi.ng/logger"></script>

Skypack documentation

For Node.js REPL:

const logger = await import("@thi.ng/logger");

Package sizes (brotli'd, pre-treeshake): ESM: 695 bytes

None

One project in this repo's /examples directory is using this package:

Screenshot	Description	Live demo	Source
	Declarative component-based system with central rstream-based pubsub event bus	Demo	Source

Generated API docs

TODO

• Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-logger,
  title = "@thi.ng/logger",
  author = "Karsten Schmidt",
  note = "https://thi.ng/logger",
  year = 2016
}

© 2016 - 2024 Karsten Schmidt // Apache License 2.0