This post was written for Nodejitsu blog and is crossposted here. Nodejitsu loved what I was doing at npmawesome.com and is now supporting the project.

stepup (GitHub: CrabDude/stepup, License: MIT) by Adam Crabtree is a simple control-flow library that makes parallel execution, serial execution, and error handling painless. This module originated as step by Tim Caswell and was pretty popular. I liked the stepup fork for the new features that it offers.

npm install stepup

Usage

The most important thing to understand about stepup is that it basically creates and keeps track of callback functions that you can then pass around. Here’s a simple example of reading the content of every file in the current directory.

var stepup = require('stepup');
var fs = require('fs');

stepup([
  function ($) {
    fs.readdir(__dirname, $.first());
  },
  function ($, files) {
    // pass down the list of files first
    $.first()(null, files);

    // create a group of `first` type of callbacks
    var stats = $.group('first');

    for (var i = 0; i < files.length; i++) {
      fs.stat(__dirname + '/' + files[i], stats());
    }
  },
  function ($, files, stats) {
    var content = $.group('first');

    for (var i = 0; i < files.length; i++) {
      if (!stats[i].isDirectory()) {
        fs.readFile(__dirname + '/' + files[i], content());
      }
    }
  },
  function ($, content) {
    return content.map(function (buf) {
      return buf.toString();
    });
  }
], function (err, content) {
  console.log(content.join('\n-----\n'));
});

What Else?

Checkout the runnable example and github example repository.