Pushing object to Array makes parameter empty

Asked Jan 31 '18 at 01:50

Active Jan 31 '18 at 01:52

Viewed 45 times

I'm trying to solve problem of merging two arrays of objects, so I wrote a pretty simple function

function mergeShowtimes(movies) {
    var existing_halls = [];

    return movies.reduce(function(acc, movie) {
        var movies_with_hallid,
            movies_seats;

        if (existing_halls.indexOf(movie.hallId) === -1) {
            movies_with_hallid = _.filter(movies, function(filter_movie) {
                return movie.hallId === filter_movie.hallId;
            });

            movies_seats = _.map(movies_with_hallid, 'seats');
            movie.seats = _.union.apply(this, movies_seats);
            acc.push(movie);
            existing_halls.push(movie.hallId);
        }

        return acc;
    }, []);
}

problem is, whenever I check the value of movie and movie.seats, field 'seats' in movie is empty, but movie.seats is not, for some reason

If I'll remove acc.push(movie); everything will start working as planned

What am I doing wrong?

Thanks for any feedback!

edited Jan 31 '18 at 01:52

Gaurang Tandon

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asked Jan 31 '18 at 01:50

Nausik

What is that _ object ? – Eric MORAND Jan 31 '18 at 02:03
@EricMORAND that's Lodash – Nausik Jan 31 '18 at 02:04
Some sample data would be helpful. – Scott Sauyet Jan 31 '18 at 02:08
where is acc initialized? – Ctznkane525 Jan 31 '18 at 02:21
@Ctznkane525: That's part of `Array.prototype.reduce`. The second argument to `movies.reduce` is `[]`, which is the initial value of `acc`. After that, it's given whatever was returned by the last iteration. – Scott Sauyet Jan 31 '18 at 02:27

Pushing object to Array makes parameter empty

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