Show some ❤️ to process errors in Node.js.

By default Node.js prints uncaughtException, warning and mishandled promises (unhandledRejection, rejectionHandled, multipleResolves) on the console which is very useful. Unfortunately those process errors:

• show neither stack traces nor promise values for warning, rejectionHandled and multipleResolves making it hard to debug.
• are inconvenient to log to an external service.
• cannot be conditionally skipped.
• are printed each time an error is repeated (except for warning).
• are not human-friendly.

log-process-errors fixes all those issues.

Without log-process-errors:

With log-process-errors:

Install

Production code (e.g. a web server) can install this either as a production or development dependency:

npm install log-process-errors

However libraries should install this as a development dependency:

npm install -D log-process-errors

This is because logging is modified globally and libraries users might not expect this side-effect. Also this might lead to conflicts between libraries.

Usage

There are two ways to load this library. The first is to use the node -r CLI flag:

node -r log-process-errors/register ...

The second is:

const logProcessErrors = require('log-process-errors')
logProcessErrors(options)

logProcessErrors() should be called as early as possible in the code.

Options

options is an optional object with the following properties:

• log {function}: override how events are logged. Default: use console.warn(), console.error(), etc.
• level {object}: which log level to use. Default: { warning: 'warn', multipleResolves: 'info', default: 'error' }.
• message {function}: override the default message generation.
• colors {boolean}: colorize the default message. Default: true.
• exitOn {string[]}: which events should trigger process.exit(1). Default: ['uncaughtException'].

Please see the options full documentation.

Full example:

logProcessErrors({
  log(message, level, info) {
    winstonLogger[level](message)
  },

  level: { multipleResolves: 'debug' },

  message(info) {},

  colors: false,

  exitOn: ['uncaughtException', 'unhandledRejection'],
})

Restoring default behavior

Node.js default behavior can be restored by firing the function returned by logProcessErrors().

const restore = logProcessErrors(options)
restore()