http_collect.js

var http = require('http');

function http_collect(url, callback) {
  http.get(url, function(resp) {
    var data = [];
    resp.setEncoding('utf8');
    resp.on('data', Array.prototype.push.bind(data));
    resp.on('end', function() {
      return callback(null, data.join(''));
    });
  }).on('error', callback);
}

module.exports = http_collect;

juggling_async.js

var http_collect = require('./http_collect');

main(process.argv.slice(2));

function main(argv) {
  this.results = [];
  this.log = DeferFor(argv.length, logResults);

  for (var i = 0; i < argv.length; i++) {
    http_collect(argv[i], addResultAt.bind(this, i));
  }
}

function addResultAt(index, err, data) {
  if (err) return this.log(err);

  this.results[index] = data;

  return this.log(null, this.results);
}

function logResults(err, data) {
  if (err) throw err;

  data.forEach(function(d) {
    console.log(d);
  });
}

// functionally equivalent to "after" - https://github.com/Raynos/after
function DeferFor(count, callback) {
  if (count <= 0) {
    return callback(new Error('Count must be greater than zero'));
  }

  return function(err, data) {
    if (err) return callback(err);

    if (--count === 0) {
      return callback(null, data);
    }

    if (count < 0) {
      return callback(new Error('Used DeferFor callback more than requested'));
    }
  };
}

juggling_async_after.js

var after = require('after');
var http_collect = require('./http_collect');

main(process.argv.slice(2));

function main(argv) {
  this.results = [];
  this.log = after(argv.length, logResults);

  for (var i = 0; i < argv.length; i++) {
    http_collect(argv[i], addResultAt.bind(this, i));
  }
}

function addResultAt(index, err, data) {
  if (err) return this.log(err);

  this.results[index] = data;

  return this.log(null, this.results);
}

function logResults(err, data) {
  if (err) throw err;

  data.forEach(function(d) {
    console.log(d);
  });
}

juggling_async_map.js

var async = require('async');
var http_collect = require('./http_collect');

async.map(process.argv.slice(2), http_collect, logResults);

function logResults(err, data) {
  if (err) throw err;

  data.forEach(function(d) {
    console.log(d);
  });
}