Get total number of likes for each user in an array of objects - JavaScript

Question

So I'm stuck with a logical problem. I'm trying to figure out a way of getting total number of likes for each user in an array of objects. Here is my Sample array.

const articles = [{
  authorId: "2vP3i2rYvDYPrikE1k1DTaZDeoq1",
  dislikes: 0,
  likes: 3,
  neutral: 0,
  text: "This is Mike Alice's first Shot!!",
  username: "mikealice",
  id: "NMFGbeTvSYddsr7VzjFV",
},
 {
  authorId: "2vP3i2rYvDYPrikE1k1DTaZDeoq1",
  dislikes: 0,
  likes: 2,
  neutral: 0,
  text: "This is Mike Alice's second Shot!!",
  username: "mikealice",
  id: "NMFGbeTvSYddsr7VzjFV",
},
 {
  authorId: "2vP3i2rYvDYPrikE1k1klkDTaZDeoq1",
  dislikes: 0,
  likes: 1,
  neutral: 0,
  text: "This is admin's first Shot!!",
  username: "admin",
  id: "NMFGbeTvSYddsr7VzjFV",
},
 {
  authorId: "2vP3i2rYvDYPrikE1k1klkDTaZDeoq1",
  dislikes: 0,
  likes: 3,
  neutral: 0,
  text: "This is admin's second Shot!!",
  username: "admin",
  id: "NMFGbeTvSYddsr7VzjFV",
}]

My goal is to have a final list of of distinct username with their total likes like the one bellow.

const userLikes = [
  {
  username: 'mikealice',
  totalLikes: 5
  },
  {
  username: 'admin',
  totalLikes: 4
  }
]

Help me figure out the logic to solving this problem. Thanks.

Answer 1

1. Take an empty object, say obj
2. Loop through your array
3. On every loop, check for if obj has already a key same as the current username
4. If not then, create a key value pair, key would be the username , value would be another object containing username and totalLikes
5. If there is already a key same as username , increase the value of totalLikes with current likes
6. After the loop is finished, you will have your answer, but in a dictionary / object form
7. Object.values will bring out the desired array

Code -

 let obj = {} articles.forEach((article, index) => { let { username, likes } = article if (!obj[username]) { obj[username] = { username, totalLikes: likes } } else { let { totalLikes } = obj[username] obj[username].totalLikes = totalLikes + likes } }) let finalArray = Object.values(obj)

Answer 2

Using reduce and Object.values will simplify.

 const getTotalLikes = arr => Object.values( arr.reduce((acc, { username, likes }) => { acc[username] = username in acc ? { username, totalLikes: acc[username].totalLikes + likes } : { username, totalLikes: likes }; return acc; }, {}) ); const articles = [ { authorId: "2vP3i2rYvDYPrikE1k1DTaZDeoq1", dislikes: 0, likes: 3, neutral: 0, text: "This is Mike Alice's first Shot!!", username: "mikealice", id: "NMFGbeTvSYddsr7VzjFV" }, { authorId: "2vP3i2rYvDYPrikE1k1DTaZDeoq1", dislikes: 0, likes: 2, neutral: 0, text: "This is Mike Alice's second Shot!!", username: "mikealice", id: "NMFGbeTvSYddsr7VzjFV" }, { authorId: "2vP3i2rYvDYPrikE1k1klkDTaZDeoq1", dislikes: 0, likes: 1, neutral: 0, text: "This is admin's first Shot!!", username: "admin", id: "NMFGbeTvSYddsr7VzjFV" }, { authorId: "2vP3i2rYvDYPrikE1k1klkDTaZDeoq1", dislikes: 0, likes: 3, neutral: 0, text: "This is admin's second Shot!!", username: "admin", id: "NMFGbeTvSYddsr7VzjFV" } ]; console.log(getTotalLikes(articles));