apache bench like tester in node

gistfile1.txt

var async = require('async');
var args = require('yargs').argv;
var request = require('request');

String.prototype.trim=function(){return this.replace(/^\s+|\s+$/g, '');};

const concurrency = args.c || 1,
  count = args.n || 100,
  data = args.d,
  verb = args.verb || 'GET',
  url = args.url;

var headers = args.h;
var array = new Array(count);
array.fill('a');

var current_count = 0;

if (!Array.isArray(headers)){
  headers = [headers];
}
var headers_obj = {};
headers.forEach(h => {
  var tmp = h.split(':');
  headers_obj[tmp[0]] = tmp[1].trim();
})
async.parallelLimit(array.map(function(){
  return function(cb){

    var time = new Date().getTime();
    var options = {
      method: verb,
      headers: headers_obj,
      timeout: 15000
    }

    if (data){
      options['body'] = data;
    }
    //console.log(options);
    request(url, options, function(err, res, body){
      current_count++;
      if (current_count % 100 == 0){
        console.log('Completed', current_count);
      }
      var diff = new Date().getTime() - time;
      if (err){
        console.log(err);
        cb(null, {
          error: err
        });
      } else {
        cb(null, {
          statusCode: res.statusCode,
          diff: diff
        });
      }
    });
  }
}), concurrency,
function(err, results){
  var success_cnt = 0;
  var sum = 0;
  results.filter(f => !f.error).forEach(item => {
    success_cnt++;
    sum += item.diff;
  })
  var avg = sum/success_cnt;
  console.log('Count:', success_cnt, 'Avg: ', avg, 'Request Per Sec:',  1000 / (avg/concurrency));
})