Async JS/Node - Sequential Promises Example - Part 1

example.js

// Part 1

function findLikesForPostsByUsername(username, callback) {
  var promise = new Promise(function(resolver, rejector) {
    findUserByUsername(username)
      .then(findPostsByUser)
      .then(findLikesByPosts)
      .then(function(likes) {
        var totalLikes = likes.reduce(function(x, y) { return x + y })
        resolver(totalLikes)
      })
      .catch(function(err) {
        rejector(err)
      })
  })
  
  return promise
}