javascript - Running async tasks in parallel

Question

In RxJS, when you want to run http requests in sequence- you chain them. But I'm not clear on how can I run requests in parallel? I saw in the examples on http://reactive-extensions.github.io/learnrx/ that they use Observable.zip() to run 2 requests in parallel. But how would you run 5 requests in parallel? More specifically, how can I setup so that my function is called:

• when all 5 complete?
• when first complete?

Answer 1

.zip() はそれを助けることができます!

const a$ = Observable.interval(200).take(6) 
const b$ = Observable.interval(300).take(10)
const c$ = Observable.interval(400).take(3)
  .zip(b$,a$)
  .subscribe(v=>console.log(v))


// marble 
-0-1-2-3-4-5|    (a$)
--0--1--2--3--4| (b$)
---0---1---2|    (c$)
  zip(a$, b$)
---[0,0,0]---[1,1,1]---[2,2,2]|

// console.log
[0,0,0]
pause(400ms)
[1,1,1]
pause(400ms)
[2,2,3]

.zip(arg1, arg2, (それ自体, arg1, arg2)=> doSomething() )

const a$ = Observable.interval(200).take(6)
const b$ = Observable.interval(300).take(10)
const c$ = Observable.interval(400).take(3)
  .zip(b$,a$, (c,b,a)=>a+b+c)
  .subscribe(v=>console.log(v))

// console.log()
0
pause(400ms)
3 = (1+1+1)
pause(400ms)
9 = (3+3+3)

または

merge() + flatMap()

import Rx, { Observable } from 'rxjs'
import axios from 'axios'

const promiseA = axios.get('https://jsonplaceholder.typicode.com/users/1')
    , promiseB = axios.get('https://jsonplaceholder.typicode.com/users/2')
    , promiseC = axios.get('https://jsonplaceholder.typicode.com/users/3')

Observable.interval(0).take(1)
  .flatMap(()=>Observable.merge(promiseA, promiseB, promiseC)) 
   // flatMap will resolve the promise for you!
  .map(res=>res.data.username)
  .reduce((arr,item)=>arr.concat(item),[])
  .subscribe(v=>console.log(v)) // [ 'Samantha', 'Antonette', 'Bret' ]

Answer 2

https://www.npmjs.org/package/asyncを見ることができます

ブラウザでも使えるノードモジュールです。