batch-resolve.js

const dns = require('dns');

// how many parallel "workers" to use
let batchSize = 3;

// domain list to process
let domains = [
    'neti.ee',
    'hot.ee',
    'zone.ee',
    'telia.ee',
    'delfi.ee',
    'postimees.ee',
    'nali.ee'
];

// function that is called once all domains have been processed
let resolved = () => {
    console.log('Kõik valmis');
};

// counter to see how many domains are currently pending resolve
let resolvePending = 0;

// "worker" function to resolve single domain name
let resolve = () => {
    if (!domains.length) {
        if (!resolvePending) {
            // all processed
            resolved();
        }
        // some requests still pending, ignore
        return;
    }
    let domain = domains.shift();
    resolvePending++;
    dns.resolveAny(domain, (err, ret) => {
        resolvePending--;
        if (err) {
            console.error(domain, err);
        } else {
            console.error(domain, ret);
        }

        // restart over with next domain name
        resolve();
    });
};

// start "workers"
for (let i = 0; i < batchSize; i++) {
    resolve();
}