https://github.com/fiverr/event-custodian

📆 Take responsibility for listeners on event emitter and look after them
https://github.com/fiverr/event-custodian

eventemitter listeners nodejs

Last synced: 7 months ago
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📆 Take responsibility for listeners on event emitter and look after them

• Host: GitHub
• URL: https://github.com/fiverr/event-custodian
• Owner: fiverr
• License: mit
• Created: 2020-09-18T06:52:50.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2023-03-21T22:55:32.000Z (over 2 years ago)
• Last Synced: 2025-04-04T18:11:53.467Z (8 months ago)
• Topics: eventemitter, listeners, nodejs
• Language: JavaScript
• Homepage:
• Size: 10.7 KB
• Stars: 3
• Watchers: 33
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE
  • Codeowners: .github/CODEOWNERS

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README

          
# event-custodian [![](https://img.shields.io/npm/v/event-custodian.svg)](https://www.npmjs.com/package/event-custodian) [![](https://img.shields.io/badge/source--000000.svg?logo=github&style=social)](https://github.com/fiverr/event-custodian) [![](https://circleci.com/gh/fiverr/event-custodian.svg?style=svg)](https://circleci.com/gh/fiverr/event-custodian)

Control handlers for an event set on an [EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)

## Usage

### TL;DR

```js

const Custodian = require('event-custodian');

new Custodian(emitter, 'event').mount().on('error', (error) => logger.error(error));

// Example: Avoid errors in events that can cause the process to exit with SIGTERM

new Custodian(process, 'unhandledRejection').mount().on('error', (error) => console.error(error));

```

## Motivation

By overriding native behaviour we can verify existing event handlers run in a safe environment, within a try/catch block. This way we can avoid unexpected results, such as the process exiting unexpectedly within an event handler. We can later decide how we want to handle these errors by placing a general onerror handler on the custodian.

## Detailed example using process and "unhandledRejection"

```js

// Reduce all existing listeners to one

const custodian = new Custodian(process, 'unhandledRejection');

// Reduce all existing listeners to one

custodian.mount();

// Handle errors coming up from registered handlers

custodian.on('error', (error) => logger.error(error));

// Add, prepend, remove event handlers as normal

process.on('unhandledRejection', console.error)

    .prependListener('unhandledRejection', (error) => { ... })

    .off('unhandledRejection', console.error)

    .removeAllListeners('unhandledRejection');

// Custodian is now managing the call stack

// Revert to native subscription functions (remove override). Reinstate all existing handlers as individual event handlers

custodian.unmount();

```

### Important note about 'unhandledRejection'

If you use this application to manage `unhandledRejection`, you **must** set an `on('error')` handler. Otherwise the custodian will simply print the errors onto `console.error`.