new EventDispenser<M>()

EventDispenser.prototype.on<K extends keyof M>(
  type: K,
  handler: (event: <M[K]>) => void,
  isAsync = false,
)

EventDispenser.prototype.once<K extends keyof M>(
  type: K,
  handler: (event: <M[K]>) => void,
  isAsync = false,
)

EventDispenser.prototype.off<K extends keyof M>(
  type: K,
  handler: (event: <M[K]>) => void,
)

EventDispenser.prototype.emit<K extends keyof M>(
  type: K,
  event: M[K]
)

import EventDispenser from 'event-dispenser'

interface EventMap {
  succeed: {
    status: 200 | 304
    data: number[]
  }
  fail: {
    status: 500 | 404
    message: string
  }
}

const dispenser = new EventDispenser<EventMap>()

function sendRequest() {
  const promise = new Promise<number[]>((resolve, reject) => {
    // send a request...
  })

  promise.then((data) => {
    dispenser.emit('succeed', {
      status: 200,
      data,
    })
  })

  promise.catch(() => {
    dispenser.emit('fail', {
      status: 500,
      message: 'request failed',
    })
  })

  return promise
}

dispenser.on('succeed', (res) => {
  // ...
})

dispenser.on('fail', (res) => {
  // ...
})