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Returning an object using reduce()

pjmantoss profile image PJ Mantoss ・1 min read

Hi good people! I need help with some JavaScript challenge:

QUESTION: Write a function called getSongCountByArtist which takes in an array of songs and returns an object. The keys in the object should be artist names, and the values should be the number of songs by that artist in the original array.

My code Solution:

function getSongCountByArtist(arr){

return arr.reduce(function(acc,val){
    let artistSong = val.name;
    let songNo = artistSong.length;

    return acc[val.artist] + songNo;

}, {})

}

getSongCountByArtist(songs); //NaN

data source https://github.com/PJMantoss/iterators2/blob/master/data.js

PROBLEM EXPLANATION: The function is supposed to return an object with artist names as keys and number of songs by the artist as values. But On running getSongCountByArtist(songs) it returns NaN. How can I refactor my code to work? Thank you

Discussion

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craigmc08 profile image
Craig McIlwrath

You're code is very close, but the function given to reduce should return an object. Instead of returning acc[val.artist] + songNo, you could increment acc[val.artist] by songNo and the return acc.

Although I'm not sure why you're adding the length of the song name. Maybe just increment by 1 each time?

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pjmantoss profile image
PJ Mantoss Author

Hi Craig! I have applied your suggestion. It's still not returning the right data. It returns an empty object. Please See below:

function getSongCountByArtist(arr){

return arr.reduce(function(acc,val){
    let artistName = val.artist,
        artistSong = val.name;

     arr[artistName] = artistSong;

    if(artistName){
        artistSong += 1;
    }

    return acc;

}, {})

}
//test
getSongCountByArtist(songs); // {}

Thank you

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craigmc08 profile image
Craig McIlwrath

Seems I didn't describe my idea very well. Here's the code I had in mind:

function getSongCountByArtist(songs) {
  return songs.reduce(function (acc, song) {
    if (acc[song.artist] === undefined) acc[song.artist] = 0;
    acc[song.artist]++;
    return acc;
  }, {});
} 
Thread Thread
pjmantoss profile image
PJ Mantoss Author

Hello Craig! I've implemented your code and it works perfectly now. Thanks a million! I appreciate your help.

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eddifd profile image
EddiFd

Do not use reduce.

Try :

Array.from(new Set(songs.map(e => e.artist).sort()).values()).map(e => {let obj = {}; obj[e] = songs.filter(f => f.artist == e).length; return obj;})