Use async series and parallel with exported function in node.js

Question

I'm trying to get my code to run using the async module. However, when the async.series runs, it only executes the third() function then stops. I understand that the first argument of async.series takes an array of tasks that requires a callback. However, I'm unsure as to how I'm supposed to do a callback on a function that I've exported from another file as in the functions first() and second(). Any help?

process.js:

var process = require('child_process');

function executeProcess() {
  process.exec(...);
}

exports.Process = function() {
  executeProcess();
}

app.js

var process = require('./process.js');

function first() {
  process.Process();
}

function second() {
  process.Process();
}

function third() {
  console.log('third');
}

function parallel() {
  async.parallel([first, second], function() {
    console.log('first and second in parallel');
  });
}

async.series([third, parallel], function() {
  console.log('third then parallel');
});

Answer 1

You should use callback functions. I think your process.js is ok so I have not changed it. But I made some minor changes in the app.js. Just added there callback functions:

var process = require('./process.js');
var async = require("async");

function first(callback) {
    console.log('FIRST');
    process.Process();
    callback();
}

function second(callback) {
    console.log('SECOND');
    process.Process();
    callback();
}

function third(callback) {
  console.log('third');
  callback();
}

function parallel() {
  async.parallel([first, second], function(callback) {
    console.log('first and second in parallel');
  });
}

async.series([third, parallel], function() {
  console.log('third then parallel');
});

This should work. Here is an very good blogpost about async library:

Node.js async in practice: When to use what?