Error thrown in event listener affects emit code

event-error.js

const EventEmitter = require('events')

const emitter = new Eventemitter()

function shouldNotThrow() {
  try {
    emitter.emit('x')
  }
  catch {
    // unfortunately, error is thrown
  }
}

emitter.on('x', () => { throw new Error('thrown') })

shouldNotThrow()

This behavior surprised me.

It makes sense (in JavaScript) but at the same time doesn't make sense.
I would assume event to be fire-and-forget.

It is not the case there because JavaScript is single threaded.

One way to mitigate this is to wrap the listener.

class FireAndForgetEmitter extends EventEmitter {
  on(event, listener) {
    const wrappedListener = (...args) => {
      try {
        listener(...args)
      }
      catch (err) {
        this.emit('error', err)
      }
    }
  }
  super.on(event, wrappedListener)
}