How to merge two arrays into one using .map and .filter

user_14775829 0
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Using two selects to database I'm returning two arrays "Movies" and "Comments" and I must to merge this arrays based on "movieId" into one and send it back to client in response.

Movies:

[
    {
        "movieId": "0DD20C53-FF5C-EB11-8140-707781834352"
    },
    {
        "movieId": "01C14AF4-3E37-EB11-8138-778184434310"
    },
]

Comments:

[
    {
        "commentId": "1",
        "movieId": "0DD20C53-FF5C-EB11-8140-707781834352",
        "content": "thanks"
    },
]

And in that case I want this result:

[
      {
        movieId: "0DD20C53-FF5C-EB11-8140-707781834352",
        comments: [
          {
            commentId: "1",
            movieId: "0DD20C53-FF5C-EB11-8140-707781834352",
            content: "thanks",
          },
        ],
      },
      {
        movieId: "01C14AF4-3E37-EB11-8138-778184434310",
        comments: [],
      },
    ];

Currently I wrote this code, but something is wrong because comment is added to both movies so something is wrong with checking movie.movieId = comment.movieId. Can someone tell me how to use .map and .filter correctly or better solution to that case? Maybe there is something better for performance.

let result = movies.map((movie) => ({
      ...movie,
      comments: comments.filter((comment) => {
        comment.movieId = movie.movieId;
      }),
    }));
typescript
1 Answers

You need to change = to === since you want to compare strings. Also add a return statement:

const result = movies.map(movie => ({
  ...movie,
  comments: comments.filter(comment => {
    return comment.movieId === movie.movieId;
  }),
}));

Or in short:

const result = movies.map(movie => ({
  ...movie,
  comments: comments.filter(comment => comment.movieId === movie.movieId),
}));
user_24366550
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