Async JS/Node - Sequential Async.js Example - Part 1

example.js

// Part 1

function findLikesForPostsByUsername(username, mainCallback) {
  async.waterfall([
    function(callback) {
      findUserByUserName(username, callback)
    },
    function(user, callback) {
      findPostsByUser(user, callback)
    },
    function(posts, callback) {
      findLikesByPosts(posts, callback)
    },
  ], function(err, likes) {
    if(err) return mainCallback(err)

    var totalLikes = likes.reduce(function(x, y) { return x + y })
    mainCallback(null, totalLikes)
  });
}