Using async-waterfall to avoid callback hell

async-waterfall.js

const waterfall = require('async-waterfall');

waterfall([
  function(callback){
    callback(null, 'one', 'two');
  },
  function(arg1, arg2, callback){
    callback(null, 'three');
  },
  function(arg1, callback){
    // arg1 now equals 'three' 
    callback(null, 'done');
  }
], function (err, result) {
  // result now equals 'done' 
});