@americanexpress/lumberjack
v1.2.0
Published
Lumberjack is a minimal, configurable Console with utilities.
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lumberjack
is a minimal and configurableConsole
with utilities.
👩💻 Hiring 👨💻
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?
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📖 Table of Contents
✨ Features
- minimal and configurable
Console
with utilities. - Log formating using
formatter
depending on the log level. - Invoke callback functions before and after writing to stream.
- Replace global
console
object using lumberjack
🤹 Usage
Installation
npm i @americanexpress/lumberjack
Invocation
How to use Lumberjack
Read more about this in the Lumberjack API section.
import Lumberjack from '@americanexpress/lumberjack';
function createLogger(simple = true) {
return new Lumberjack({
formatter: simple
// your formatter function can be as simple as:
? (level, ...args) => `${level}: ${args}`
// or can be more complex, like stringifying as JSON:
: (level, ...messages) => JSON.stringify(
{
level,
messages,
time: new Date().toISOString(),
},
null,
2
),
});
}
const logger = createLogger();
logger.error(new Error('sample error'));
logger.warn("you're gonna have a bad time");
logger.info('%d', 42);
logger.log({ its: 'complicated' });
logger.dir(document.location); // lists properties of an object
logger.table(['apples', 'oranges', 'bananas']); // expects array
How to use monkeypatches
Read more about this in the monkeypatches API section.
import Lumberjack, { monkeypatches } from '@americanexpress/lumberjack';
const logger = new Lumberjack();
monkeypatches.replaceGlobalConsole(logger);
console.log('This is now invoking logger.log');
🎛️ API
Lumberjack
Creating a new console/Lumberjack is similar to creating a new nodejs Console, but slightly different:
- pass a single object with named options
const logger = new Lumberjack({
// options are added here
});
Options
are:
stdout
: stream to write to, defaults toprocess.stdout
stderr
: defaults to thestdout
optionformatter
: an optional function that gets the log level and raw input arguments to return a string that is written to the stream (eitherstdout
orstderr
depending on log level)- defaults to
util.format
(nodejs Console's formatter) - can return
null
to skip writing to the stream
- defaults to
beforeWrite
: callback function invoked before writing to the streamafterWrite
: callback function invoked after writing to the stream
The Lumberjack
instance has four methods: error
, warn
, info
, and log
.
monkeypatches
A monkey patch is a way for a program to extend or modify supporting system software locally (affecting only the running instance of the program).
https://en.wikipedia.org/wiki/Monkey_patch
Use monkeypatches with care and be aware of pitfalls.
replaceGlobalConsole
Replaces the error
, warn
, info
, and log
methods on the global console
object with those of the logger
argument provided.
import Lumberjack, { monkeypatches } from '@americanexpress/lumberjack';
const logger = new Lumberjack();
monkeypatches.replaceGlobalConsole(logger);
console.log('This is now invoking logger.log');
attachSpy
Spy on invocations of methods, ex: on native packages.
Arguments:
- object the method exists on
- method name to spy on
- spy function, receives
- an array of the original arguments
- a function to invoke the original method and get the return value, this will be invoked automatically if not done by the spy function
See also attachHttpRequestSpy and attachHttpsRequestSpy
import { monkeypatches } from '@americanexpress/lumberjack';
monkeypatches.attachSpy(http, 'request', (args, callOriginal) => {
console.log('starting http request', args);
const returnValue = callOriginal(); // spy, not an interceptor, so args handled automatically
console.log('http request started', returnValue);
});
attachHttpRequestSpy
Spy on the beginning and end of an http.request
.
Arguments:
- spy for the invocation of
http.request
- spy for the close of the socket used in the
http.request
Both spies receive the return value of http.request
and a normalized parsed URL requested (via url.parse
).
import { monkeypatches } from '@americanexpress/lumberjack';
monkeypatches.attachHttpRequestSpy(
(clientRequest, parsedUrl) => console.info(`started request to ${parsedUrl.href}`),
(clientRequest, parsedUrl) => console.info(`request to ${parsedUrl.href} finished`)
);
attachHttpsRequestSpy
The same thing as attachHttpRequestSpy but for the https
native package.
Note that for nodejs versions before 6.0.0 and earlier https.request
called http.request
so adding spys for both
http
and https
will result in both spies being called.
🏆 Contributing
We welcome Your interest in the American Express Open Source Community on Github. Any Contributor to any Open Source Project managed by the American Express Open Source Community must accept and sign an Agreement indicating agreement to the terms below. Except for the rights granted in this Agreement to American Express and to recipients of software distributed by American Express, You reserve all right, title, and interest, if any, in and to Your Contributions. Please fill out the Agreement.
Please feel free to open pull requests and see CONTRIBUTING.md to learn how to get started contributing.
🗝️ License
Any contributions made under this project will be governed by the Apache License 2.0.
🗣️ Code of Conduct
This project adheres to the American Express Community Guidelines. By participating, you are expected to honor these guidelines.