Wait for all event subscribers to complete their event processing

await-all-subscriber-completion.js

"use strict"

var events = require("events")
var ev = new events.EventEmitter()
var log = console.log.bind(console)
process.on('unhandledRejection', function(reason, p) {
  log(`Possibly Unhandled Rejection at: Promise ${p} reason: ${reason}`)
})
process.on('uncaughtException', function(err) {
  log(`Caught exception: ${err}`)
})


class API {
  static load(timeout) {
    return new Promise(function(res) {
      setTimeout(res, timeout)
    })
  }
  static save(timeout) {
    return new Promise(function(res) {
      setTimeout(res, timeout)
    })
  }
}

class PromiseAll {
  constructor(){
    this.all = [];
  }
  add() {
    var resolver;
    this.all.push(new Promise(function(res){
      resolver = res
    }))
    return resolver
  }
  waitAll() {
    return Promise.all(this.all)
  }
}

ev.on("changed", function(waitAll) {
  log("#1 rec changed")
  var one = waitAll.add()
  API.load(4000).then(function() {
    log("#1 done")
    one()
  })
})

ev.on("changed", function(waitAll) {
  log("#2 rec changed")
  var one = waitAll.add()
  API.load(2000).then(function() {
    log("#2 done")
    one()
  })
})


var waitAll = new PromiseAll()
ev.emit("changed", waitAll)

API.save(1000).then(function() {
  log("changes saved")
  waitAll.waitAll().then(function() {
    log("all subscribers handled event")
  })
})