Filtering an array of objects that contain arrays

Question

This is a smaller version of the array i have but it has the same structure

with const arr below, i want to create 2 new arrays with unique values that are sorted in ascending order

const arr = [{
    tags: ['f', 'b', 'd'],
    weight: 7,
    something: 'sdfsdf'
  },
  {
    tags: ['a', 'b', 'c', 'd', 'e'],
    weight: 6,
    something: 'frddd'
  },
  {
    tags: ['f', 'c', 'e', 'a'],
    weight: 7,
    something: 'ththh'
  },
  {
    tags: ['a', 'c', 'g', 'e'],
    weight: 5,
    something: 'ghjghj'
  }
];

const finalTags = [];
const finalWeight = [];

// TODO:  find a better way to do this
arr.forEach(v => {
  if (finalWeight.indexOf(v.weight) === -1) finalWeight.push(v.weight);
  v.tags.forEach(val => {
    if (finalTags.indexOf(val) === -1) finalTags.push(val);
  });
});

// Ascending order
finalTags.sort();
finalWeight.sort();

what i have above works, but seems a bit messy and was wandering if there was a better/tidier way of doing this

Might this be better off on codereview.stackexchange.com?

rh16
– rh16

2019-03-08 05:18:37 +00:00
Commented Mar 8, 2019 at 5:18 — rh16
– rh16, Commented Mar 8, 2019 at 5:18

Yosvel Quintero · Accepted Answer · 2019-03-09 01:41:41Z

2

You can use Array.prototype.reduce() combined with Set in order to get an object with the sorted arrays {tags: [], weights: []}:

const arr = [{tags: ['f', 'b', 'd'],weight: 7,something: 'sdfsdf'},{tags: ['a', 'b', 'c', 'd', 'e'],weight: 6,something: 'frddd'},{tags: ['f', 'c', 'e', 'a'],weight: 7,something: 'ththh'},{tags: ['a', 'c', 'g', 'e'],weight: 5,something: 'ghjghj'}];
const obj = arr.reduce((a, {tags, weight}) => {
  a.tags = [...new Set(a.tags.concat(tags))];
  a.weights = [...new Set(a.weights.concat(weight))];
  return a;
}, {tags: [], weights: []});

// final result i want
console.log('finalTags:', obj.tags.sort()); // ['a', 'b', 'c', 'd', 'e', 'f', 'g'];
console.log('finalWeight:', obj.weights.sort()); // [5, 6, 7];

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Mar 9, 2019 at 1:41

answered Mar 8, 2019 at 5:16

Yosvel Quintero

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3 Comments

Shidersz Over a year ago

I will vote you up because you had a similar idea to mine and was first. However, it will be nice to see some explanation too.

Yosvel Quintero Over a year ago

Thank you for your comment @Shidersz. I have added a better description and you also have my up..

ace2case Over a year ago

much nicer than my version, thanks for all your answers

Shidersz · Accepted Answer · 2019-03-08 05:21:59Z

One solution is to use Array.reduce() to create two sets, one with the tags and other with the weights. After this you can transform the sets to arrays and use Array.sort() on they:

const arr = [
  {
    tags: ['f', 'b', 'd'],
    weight: 7,
    something: 'sdfsdf'
  },
  {
    tags: ['a', 'b', 'c', 'd', 'e'],
    weight: 6,
    something: 'frddd'
  },
  {
    tags: ['f', 'c', 'e', 'a'],
    weight: 7,
    something: 'ththh'
  },
  {
    tags: ['a', 'c', 'g', 'e'],
    weight: 5,
    something: 'ghjghj'
  }
];

let res = arr.reduce((acc, {tags, weight}) =>
{
    acc.tags = new Set([...acc.tags, ...tags]);
    acc.weights.add(weight);
    return acc;
}, {tags: new Set(), weights: new Set()});

let sortedWeigths = [...res.weights].sort();
let sortedTags = [...res.tags].sort((a, b) => a.localeCompare(b));
console.log("weights: ", sortedWeigths, "tags: ", sortedTags);

.as-console {background-color:black !important; color:lime;}
.as-console-wrapper {max-height:100% !important; top:0;}

Aniket G · Accepted Answer · 2019-03-08 05:30:28Z

You could use the following code. This basically splits arr up into finalTags and finalWeights.

.flat() flattens the array ([1, [2, [3]]] would become [1, 2, 3])

finalTags.filter((item, index) => finalTags.indexOf(item) >= index).sort(); remove's the duplicates.

const arr = [{
    tags: ['f', 'b', 'd'],
    weight: 7,
    something: 'sdfsdf'
  },
  {
    tags: ['a', 'b', 'c', 'd', 'e'],
    weight: 6,
    something: 'frddd'
  },
  {
    tags: ['f', 'c', 'e', 'a'],
    weight: 7,
    something: 'ththh'
  },
  {
    tags: ['a', 'c', 'g', 'e'],
    weight: 5,
    something: 'ghjghj'
  }
];

let finalTags = arr.map(e => e.tags);
finalTags = finalTags.flat();
finalTags = finalTags.filter((item, index) => finalTags.indexOf(item) >= index).sort();

let finalWeight = arr.map(e => e.weight);
finalWeight = finalWeight.filter((item, index) => finalWeight.indexOf(item) >= index).sort();

console.log(finalTags);
console.log(finalWeight);

Sources:

Removing duplicates: https://gomakethings.com/removing-duplicates-from-an-array-with-vanilla-javascript/

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