@patrtorg/asperiores-rerum NPM

electron-log

Simple logging module Electron/Node.js/NW.js application. No dependencies. No complicated configuration.

By default, it writes logs to the following locations:

on Linux: ~/.config/{app name}/logs/main.log
on macOS: ~/Library/Logs/{app name}/main.log
on Windows: %USERPROFILE%\AppData\Roaming\{app name}\logs\main.log

Installation

Starts from v5, electron-log requires Electron 13+ or Node.js 14+. Feel free to use electron-log v4 for older runtime. v4 supports Node.js 0.10+ and almost any Electron build.

Install with npm:

npm install electron-log

Usage

Main process

import log from 'electron-log/main';

// Optional, initialize the logger for any renderer process
log.initialize();

log.info('Log from the main process');

Renderer process

If a bundler is used, you can just import the module:

import log from 'electron-log/renderer';
log.info('Log from the renderer process');

This function uses sessions to inject a preload script to make the logger available in a renderer process.

Without a bundler, you can use a global variable __electronLog. It contains only log functions like info, warn and so on.

There are a few other ways how a logger can be initialized for a renderer process. Read more.

Node.js and NW.js

import log from 'electron-log/node';
log.info('Log from the nw.js or node.js');

electron-log v2.x, v3.x, v4.x

If you would like to upgrade to the latest version, read the migration guide and the changelog.

Log levels

electron-log supports the following log levels:

error, warn, info, verbose, debug, silly

Transport

Transport is a simple function which does some work with log message. By default, two transports are active: console and file.

You can set transport options or use methods using:

log.transports.console.format = '{h}:{i}:{s} {text}';

log.transports.file.getFile();

Each transport has level and transforms options.

Console transport

Just prints a log message to application console (main process) or to DevTools console (renderer process).

Options

format, default '%c{h}:{i}:{s}.{ms}%c › {text}' (main), '{h}:{i}:{s}.{ms} › {text}' (renderer)
level, default 'silly'
useStyles, force enable/disable styles

File transport

The file transport writes log messages to a file.

Options

format, default '[{y}-{m}-{d} {h}:{i}:{s}.{ms}] [{level}] {text}'
level, default 'silly'
resolvePathFn function sets the log path, for example

log.transports.file.resolvePathFn = () => path.join(APP_DATA, 'logs/main.log');

IPC transport

It displays log messages from main process in the renderer's DevTools console. By default, it's disabled for a production build. You can enable in the production mode by setting the level property.

Options

level, default 'silly' in the dev mode, false in the production.

Remote transport

Sends a JSON POST request with LogMessage in the body to the specified url.

Options

level, default false
url, remote endpoint

Disable a transport

Just set level property to false, for example:

log.transports.file.level = false;
log.transports.console.level = false;

Override/add a custom transport

Transport is just a function (msg: LogMessage) => void, so you can easily override/add your own transport. More info.

Third-party transports

Datadog

Overriding console.log

Sometimes it's helpful to use electron-log instead of default console. It's pretty easy:

console.log = log.log;

If you would like to override other functions like error, warn and so on:

Object.assign(console, log.functions);

Colors

Colors can be used for both main and DevTools console.

log.info('%cRed text. %cGreen text', 'color: red', 'color: green')

Available colors:

unset (reset to default color)
black
red
green
yellow
blue
magenta
cyan
white

For DevTools console you can use other CSS properties.

Catch errors

electron-log can catch and log unhandled errors/rejected promises:

log.errorHandler.startCatching(options?);

More info.

Electron events logging

Sometimes it's helpful to save critical electron events to the log file.

log.eventLogger.startLogging(options?);

By default, it save the following events:

certificate-error, child-process-gone, render-process-gone of app
crashed, gpu-process-crashed of webContents
did-fail-load, did-fail-provisional-load, plugin-crashed, preload-error of every WebContents. You can switch any event on/off.

More info.

Hooks

In some situations, you may want to get more control over logging. Hook is a function which is called on each transport call.

(message: LogMessage, transport: Transport, transportName) => LogMessage

More info.

Multiple logger instances

You can create multiple logger instances with different settings:

import log from 'electron-log/main';

const anotherLogger = log.create({ logId: 'anotherInstance' });

Be aware that you need to configure each instance (e.g. log file path) separately.

Logging scopes

import log from 'electron-log/main';
const userLog = log.scope('user');

userLog.info('message with user scope');
// Prints 12:12:21.962 (user) › message with user scope