Async JS/Node - Sequential Promises Example

example.js

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
}

var username = 'seanghagstrom'
 
findLikesForPostsByUsername(username)
  .then(function(totalLikes) {
    console.log(username + ' total number of likes: ' + totalLikes)
  })
  .catch(function(err) {
    console.error(err)
  })
})