@multipart/form-data/src/lib/counter.js

Multipart/Form-Data And File Upload Middleware For Koa Written In ES6 And Optimised With JavaScript Compiler.

import { EventEmitter } from 'events'

export default class Counter extends EventEmitter {
  constructor() {
    super()
    this.value = 0
  }
  increment () {
    this.value++
  }
  decrement () {
    if (--this.value === 0) this.emit('zero')
  }
  isZero () {
    return (this.value === 0)
  }
  onceZero(fn) {
    if (this.isZero()) return fn()

    this.once('zero', fn)
  }
  async awaitZero() {
    await new Promise((r, j) => {
      this.onceZero(r)
      this.once('error', j)
    })
  }
}