hzzzzl

div.innerHTML += responseFromServer

[...div.querySelectorAll('.some-class-name')].forEach(d => d.classList.add('new-class-name'))

data = [
  {"name":"Adhi Kot","id":"379","nametype":"Valid","recclass":"EH4","mass":"4239","fall":"Fell","year":"1919-01-01T00:00:00.000","reclat":"32.100000","reclong":"71.800000","geolocation":{"type":"Point","coordinates":[71.8,32.1]}},
  {"name":"Adzhi-Bogdo (stone)","id":"390","nametype":"Valid","recclass":"LL3-6","mass":"910","fall":"Fell","year":"1949-01-01T00:00:00.000","reclat":"44.833330","reclong":"95.166670","geolocation":{"type":"Point","coordinates":[95.16667,44.83333]}}
]

const find = (rec, key) => (data.find(v => v.recclass === rec) || {})[key]

find('EH4', 'mass')
// 4239

for ( let i=0; i<100; i++ ){
    setTimeout(function(){
      info.innerText +=  i + ', ';
    }, i * 200 );   // 0 200 400 600 ...
  }

const express = require('express')
const app = express()
const server = require('http').createServer(app)
const io = require('socket.io')(server)

app.use('/', function(request, response, next) {
  request.io = io
  next()
})

............

router.post('/', async (req, res) => {
    const { socketId } = req.body
    req.io.to(socketId).emit('fetchstart')   // всё ок
.....

function perf(fn) {
  const t1 = performance.now()
  for(let i = 0; i < 100000; i++) {
    fn()
  }
  console.log(performance.now() - t1 + ' ms')
}

ar = [...Array(10000).keys()]

function f1() {
  for (let i = 0, y = ar.length; i < y; i++) { ar[i] = ++ar[i] }
}

function f2() {
  for (let i = 0 ; i < ar.length; i++) { ar[i] = ++ar[i] }
}

perf(f1)

perf(f2)