nerdloggerjs 0.2.0
Install from the command line:
Learn more about npm packages
$ npm install @app-nerds/nerdloggerjs@0.2.0
Install via package.json:
"@app-nerds/nerdloggerjs": "0.2.0"
About this version
A simple, no dependency, configurable logger for NodeJS.
Add the following line to your .npmrc file.
@app-nerds:registry=https://npm.pkg.github.com
Add the following to your .yarnrc file.
"@app-nerds:registry" "https://npm.pkg.github.com"
yarn install @app-nerds/nerdloggerjsBasic usage is simple.
const { Logger } = require("nerdloggerjs");
const logger = new Logger();
logger.debug("this is a test");
logger.info("test #2");
logger.error("this error has additional metadata", {
who: "Adam",
message_id: "abcdefg",
});
// Output would be:
// {"time":"2022-02-02T20:57:11.821Z","level":"debug","msg":"this is a test"}
// {"time":"2022-02-02T20:57:11.824Z","level":"info","msg":"test #2"}
// {"time":"2022-02-02T20:57:11.825Z","level":"error","msg":"oh no!","who":"Adam","message_id":"abcdefg"}Nerd Logger support what you'd expect for log levels. You can configure the logger to only write a log entry if it is equal to or higher than a minimum log level. So for example, if you don't want to see debug logs in your production system you would configure your logger like so.
const { Logger, LogLevels } = require("nerdloggerjs");
const logger = new Logger(LogLevels.INFO);
logger.debug("this one won't show up");
logger.info("this one will");Valid levels are:
- DEBUG
- INFO
- WARN
- ERROR
- FATAL
By default logs are written to the console. This is done by the default writer, which is ConsoleWriter. You can however create your own writer to do what you want. A writer must implement the following methods:
- debug
- info
- warn
- error
- fatal
Each method is responsible for performing the write action. This could be sending the log entry to a file, or to a third party service. Whatever you want. When done you must call the callback method. If you provide an argument to the callback method, this will be treated as an error. Here is an example that prepends all log entries with HA! - .
const { Logger, LogLevels } = require("nerdloggerjs");
class ExampleWriter {
constructor() {}
debug(message, callback) {
console.log(`HA! - ${message}`);
callback();
}
info(message, callback) {
console.info(`HA! - ${message}`);
callback();
}
warn(message, callback) {
console.warn(`HA! - ${message}`);
callback();
}
error(message, callback) {
console.error(`HA! - ${message}`);
callback();
}
fatal(message, callback) {
console.error(`HA! - ${message}`);
callback();
}
}
const logger = new Logger(LogLevels.DEBUG, [new ExampleWriter()]);
logger.debug("this is a test");
logger.info("test #2");
logger.error("oh no!", {
who: "Adam",
message_id: "abcdefg",
});
// Output would be:
// HA! - {"time":"2022-02-02T20:45:43.649Z","level":"debug","msg":"this is a test"}
// HA! - {"time":"2022-02-02T20:45:43.653Z","level":"info","msg":"test #2"}
// HA! - {"time":"2022-02-02T20:45:43.653Z","level":"error","msg":"oh no!","who":"Adam","message_id":"abcdefg"}By default all log entries are in JSON format. This is not only human-readable, but also machine-readable, which is useful for log aggregation and searching.
You can customize the built-in JSON formatter a little bit. Let's say you didn't like the default key names for the time, level, and message. Here's how you would change it.
const { Logger, LogLevels, JSONFormatter } = require("./dist/logger.js");
const formatConfig = {
timestamp: "when",
level: "how high",
message: "payload",
};
const formatter = new JSONFormatter(formatConfig);
const logger = new Logger(LogLevels.DEBUG);
logger.format = formatter;
logger.debug("this is a test");
logger.info("test #2");
logger.error("oh no!", {
who: "Adam",
message_id: "abcdefg",
});
// Output would be:
// {"when":"2022-02-02T20:52:54.913Z","how high":"debug","payload":"this is a test"}
// {"when":"2022-02-02T20:52:54.917Z","how high":"info","payload":"test #2"}
// {"when":"2022-02-02T20:52:54.917Z","how high":"error","payload":"oh no!","who":"Adam","message_id":"abcdefg"}You can also create your own formatter. Here's an example where log entries are plain text, tab separated.
const { Logger, LogLevels, BaseFormat, now } = require("./dist/logger.js");
class TextFormatter {
constructor(config = BaseFormat) {
this.config = config;
}
format(message = "", level = LogLevels.DEBUG, metadata = {}) {
let payload = {};
payload[this.config.timestamp] = now();
payload[this.config.level] = level.text;
payload[this.config.message] = message;
for (const key in metadata) {
payload[key] = metadata[key];
}
let result = [];
for (const key in payload) {
result.push(`${key}=${payload[key]}`);
}
return result.join("\t");
}
}
const logger = new Logger(LogLevels.DEBUG);
logger.format = new TextFormatter();
logger.debug("this is a test");
logger.info("test #2");
logger.error("oh no!", {
who: "Adam",
message_id: "abcdefg",
});
// Output would be:
// time=2022-02-02T21:04:21.230Z level=debug msg=this is a test
// time=2022-02-02T21:04:21.233Z level=info msg=test #2
// time=2022-02-02T21:04:21.234Z level=error msg=oh no! who=Adam message_id=abcdefgMIT License
Copyright (c) 2022 App Nerds
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
