electron-log

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';

// Initialize the logger to be available in renderer process
log.initialize();

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

Renderer process

If a bundler is used, you can import the module in a renderer code:

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

Preload script

To use the logger inside a preload script, use the electron-log/renderer import.

There's also the electron-log/preload entrypoint, but it's used only as a bridge between the main and renderer processes and doesn't export a logger. In most cases, you don't need this preload entrypoint.

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

Read more about console transport.

File transport (main process only)

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');

Read more about file transport.

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.

In the renderer process, this transport does the opposite: it sends the data to the main process via IPC. Then, the data is written to the console and the filesystem.

Options

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

Remote transport (main process only)

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

Options

• level, default false
• url, remote endpoint

Read more about remote transport.

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
• gray

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

By default, scope labels are padded in logs. To disable it, set
log.scope.labelPadding = false.

Buffering

It's like a transaction, you may add some logs to the buffer and then decide whether to write these logs or not. It allows adding verbose logs only when some operations failed.

import log from 'electron-log/main';

log.buffering.begin();
try {
  log.info('First silly message');
  // do somethings complex
  log.info('Second silly message');
  // do something else
   
  // Finished fine, we don't need these logs anymore
  log.buffering.reject();
} catch (e) {
  log.buffering.commit();
  log.warn(e);
}

Related

• electron-cfg - Settings for your Electron application.

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