wait-for-event-emitter-promises.ts

test('events', async() => {
  const { EventEmitter } = require('events')

  const ee = new EventEmitter()

  

  const handler = (breadcrumb: string, delay: number) => 
    (promises: Promise<unknown>[]) => {
      promises.push(new Promise(resolve => {
        setTimeout(() => resolve(breadcrumb), delay)
      }))
    }

  ee.on('thing', handler('a', 0) )
  ee.on('thing', handler('b', 100) )
  ee.on('thing', handler('c', 0) )
  ee.on('thing', handler('d', 3 * 1000) )


  const promises: Promise<unknown>[] = []
  ee.emit('thing', promises)
  console.log({promises}, promises[0] instanceof Promise)
  
  const results = await Promise.all(promises)
  console.log({results})
})

  console.log
    {
      promises: [
        Promise { <pending> },
        Promise { <pending> },
        Promise { <pending> },
        Promise { <pending> }
      ]
    } true
    
    
      console.log
    { results: [ 'a', 'b', 'c', 'd' ] }
    ```