2D Array Filter based on hash key

Question

Output: User Ruby watched Transit and Max also watched the same movie and gave rating above 3. So User ruby recommendation has to be Max Jurassic Park and not weekend away userRecommend("Ruby", ratings) => ["Jurassic Park"]

How do i get the ouput for below?

const userRating = [
['David', 'Weekend Away' , 5],
['Shell', 'Frozen', '5'],
['Max', 'Jurassic Park', '5'],
['Ruby', 'Transit', '4'],
['Ruby', 'Inception', '4'],
['Max', 'Transit', '5']
['Max', 'Weekend Away', '1']
]

const userRecommendation = (user, userRating) =>{


const hash = {};
for(let i=0; i< userRating.length; i++){
    if(userRating[i][2] >=4){
      if(!hash[userRating[i][0]]){
     hash[userRating[i][0]] = [userRating[i][1]];
      }else {
 hash[userRating[i][0]].push(userRating[i][1]);
      }
      
  }
}
let userMovie = hash[user];
 
let result =[];
for(let key of Object.keys(hash)){
  
  // Need to find a way to filter
  
}


}
console.log(userRecommendation('Ruby', userRating));

Does this answer your question? https://stackoverflow.com/questions/9206914/how-to-filter-multidimensional-javascript-array — Rani Giterman, Mar 05 '22 at 16:51

Nina Scholz · Accepted Answer · 2022-03-05T17:37:36.443

You could collect all user/movie and movie/user relations in two hash tables and get the users who have rated the same movie.

The get from the users the other movies, take only unique movies and filter the rated out.

const
    userRecommendation = (user, ratings) => {
        const
            users = {},
            movies = {},
            result = [];
            
        for (const [u, m, r] of ratings) {
            if (r < 4) continue;
            (users[u] ??= []).push(m);
            (movies[m] ??= []).push(u);
        }

        for (const movie of users[user]) {
            for (const u of movies[movie]) {
                if (u !== user) result.push(...users[u]);
            }
        }
        
        return [...new Set(result)].filter(m => !users[user].includes(m));
    },
    userRating = [['David', 'Weekend Away', 5], ['Shell', 'Frozen', 5], ['Max', 'Jurassic Park', 5], ['Ruby', 'Transit', 4], ['Ruby', 'Inception', 4], ['Max', 'Transit', 5], ['Max', 'Weekend Away', 1]];

console.log(userRecommendation('Ruby', userRating));

2D Array Filter based on hash key

1 Answers1