Agfdhyk

Basically, I'm making a small script to check the IP of some servers based on their hostname, then compare that IP to a list based on the IP block a router is issuing.

The problem I'm having is clearly with the code executing asynchronously, and it's likely been answered a thousand times, but I can't seem to wrap my head around how to fix it. I've tried wrapping everything in promises but I end up breaking everything. Here is the latest attempt to break the steps I need out into individual functions.

const dns = require('dns');

const Table = require('cli-table');

const hosts = ['Server01', 'Server02', 'Server03'];

let list = ;



table = new Table({

    head: ['Host', 'Location']

    , colWidths: [20, 30]

});



function process() {

    hosts.forEach(host => {

        dns.lookup(host, function (err, result) {

            ipSplit = result.split(".");

            r = ipSplit[0] + '.' + ipSplit[1] + '.' + ipSplit[2];

            if (r == '10.23.13') {

                list.push([host, 'Lab A112']);

            }

            else {

                list.push([host, 'Unknown']);

            }

        });

    });

};



function build () {

    table.push(list);

};



function push () {

    console.log(table.toString());

};



process();

build();

push();

What piece of the puzzle am I missing here?

You'll want to use Promise.all:

const result = Promise.all(hosts.map(host => {

  return new Promise((resolve, reject) => {

    dns.lookup(host, function (err, result) {

      if (err) reject(err);

      const ipSplit = result.split(".");

      const r = ipSplit[0] + '.' + ipSplit[1] + '.' + ipSplit[2];

      if (r === '10.23.13') {

        resolve([host, 'Lab A112']);

      } else {

        resolve([host, 'Unknown']);

      }

    });

  }

}));

You can order your function calls with async/await and you will get the order you need.

const dns = require('dns');

const Table = require('cli-table');

const hosts = ['Server01', 'Server02', 'Server03'];

let list = ;



table = new Table({

    head: ['Host', 'Location']

    , colWidths: [20, 30]

});



function process() {

  return new Promise((resolve, reject) => {

    hosts.forEach(host => {

        dns.lookup(host, function (err, result) {

            ipSplit = result.split(".");

            r = ipSplit[0] + '.' + ipSplit[1] + '.' + ipSplit[2];

            if (r == '10.23.13') {

                resolve(list.push([host, 'Lab A112']));

            }

            else {

                reject(list.push([host, 'Unknown']));

            }

        });

    });

  }) 

};



function build () {

  return new Promise((resolve, reject)=>{

    resolve(table.push(list);)

  })



};



function push () {

    console.log(table.toString());

};

async function waitForFunctions() {

  try{

    const resOne = await process();

    const resTwo = await build()

  } catch(error){

    console.log(error);

  }

  return Promise.all([resOne, resTwo])

}

waitForFunctions()

.then((values)=>{

  console.log(values);

  console.log(push());

});