Welcome to Log Magic.

This project is stable. It is used in production by various companies.

The goal is to have a fast and easy to use logging subsystem that can be dynamically reconfigured to provide insight into production systems. It supports being used from within a normal Node.js, Electron Application, or in a Web Browser (via Browserify).

Logmagic does its magic by generating objects with generated functions that are only modified when the logging system is reconfigured, thus your entire logging path is contained within long-lived functions that v8/JS engines are able to JIT.

Getting Started

If you had a file named like, "lib/foo/bar.js", at the top of it, you would put the following:

var log = require('logmagic').local('mylib.foo.bar');

Then inside bar.js, you would just use the logger like any normal logger:

log.info("Hello!")
log.error("By default, format strings are not used.", {SOME_VAR: "myvalue"})
log.errorf("Just add 'f' to any log method, and you get format strings too: ${SOME_VAR}", {SOME_VAR: "myvalue"})

In any other part of your application, you can reconfigure the logging subsystem at runtime, making it easy to change log levels for specific modules dynamically.

var logmagic = require('logmagic');
logmagic.registerSink("mysink", function(module, level, message) { console.log(message); });

/* Send Info an higher in the root logger to stdout */
logmagic.route("__root__", logmagic.INFO, "stdout")

/* Reconfigure all children of mylib to log all debug messages to your custom sink */
logmagic.route("mylib.*", logmagic.DEBUG, "mysink")

Builtin sinks include: