Like multithreading Node

multi.js

const crypto = require('crypto')

const arr = new Array(200).fill('something')
function processChunk() {
  if (arr.length === 0) {
    // code that runs after the whole array is executed
  } else {
    console.log('processing chunk');
    // pick 10 items and remove them from the array
    const subarr = arr.splice(0, 10)
    for (const item of subarr) {
      // do heavy stuff for each item on the array
      doHeavyStuff(item)
    }
    // Put the function back in the queue
    setImmediate(processChunk)
  }
}

processChunk()

function doHeavyStuff(item) {
  crypto.createHmac('sha256', 'secret').update(new Array(10000).fill(item).join('.')).digest('hex')
}

// This is just for confirming that we can continue
// doing things
let interval = setInterval(() => {
  console.log('tick!')
  if (arr.length === 0) clearInterval(interval)
}, 0)