Async Request Handling in Node with Counting Callbacks

juggling-async.js

// this node program takes 3 URLs provided by the first 3 command line arguments and gets some data from those URLS. 
// the program then prints each set of data in the order it was called. 
// counting callbacks was a requirement as a method to handle the asyncronicity. 

const http = require('http');

const urls = [];
const dataArr = [];
let count = 0;

// create the URL array 

for (let i = 2; i < process.argv.length; i++) {
        urls.push(process.argv[i]);
}

function httpGet(index) {
       // variable declaration every call to empty the string. 
        let chunk = '';
        
        // send a get request to each url in the array and wait for a response. 
        http.get(urls[index], response => {
                response.on('error', console.error);
                
                // set the response object to recieve as a string with utf8 encoding. 
                response.setEncoding('utf8').on('data', data => {
                       
                        // concatenate the incoming string into a variable. 
                        chunk += data.concat('');
                });
                
                // when the URL response is done, then add the string into the array, in order.
                response.on('end', () => {
                        count += 1;
                        dataArr[index] = chunk;
                        
                        // if 3 callbacks have fininshed then loop over the array and log each item. 
                        if (count === 3) {
                                for (let i = 0; i < dataArr.length; i += 1) {
                                        console.log(dataArr[i]);
                                }
                        }
                });
        }).on('error', console.error);
}

// call the function for the number of URLs provided in the process.argv array. 

for (let i = 0; i < urls.length; i++) {
        httpGet(i);
}