Example of how to consume multiple Web APIs in parallel via Node.js Streams

concat-streams.mjs

// npm i axios stream-concat
import { pipeline } from 'stream/promises'
import StreamConcat from 'stream-concat'

import axios from 'axios'
const API_01 = 'http://localhost:3000'
const API_02 = 'http://localhost:4000'

const streams = (await Promise.all([
    axios({
        method: 'get',
        url: API_01,
        responseType: 'stream'
    }),
    axios({
        method: 'get',
        url: API_02,
        responseType: 'stream'
    })
])).map(({ data }) => data)

const stream = new StreamConcat(streams)
await pipeline(
    stream,
    async function* output(stream) {
        stream.setEncoding('utf8')
        for await (const data of stream) {
            console.log(data)
        }
    }
)

webapi.mjs

import http from 'http'
import { Readable } from 'stream'
import { pipeline } from 'stream/promises'

const handler = (apiName) => async function (request, response) {
    let count = 0;
    const maxItems = 99
    const readable = Readable({
        read() {
            const everySecond = (intervalContext) => () => {
                if (count++ <= maxItems) {
                    this.push(JSON.stringify({ id: Date.now() + count, name: `Erick-${count}`, apiName }) + "\n")
                    return;
                }
                clearInterval(intervalContext)
                this.push(null)
            }

            setInterval(everySecond(this))
        },
    })

    await pipeline(readable, response)
}

http.createServer(handler('api01')).listen(3000, () => console.log('server running at 3000'))
http.createServer(handler('api02')).listen(4000, () => console.log('server running at 4000'))