Filtering an array of objects that contain arrays

manpreet Best Answer 2 years ago

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

manpreet 2 years ago

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;}

manpreet 2 years ago

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])

And finally, [...new Set(finalTags)].sort() gets rid of duplicates and sorts the array.

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: f="https://forum.tuteehub.com/tag/5">5,
    something: 'ghjghj'
  }
];

let finalTags = arr.map(e => e.tags);
finalTags = finalTags.flat();
finalTags = [...new Set(finalTags)].sort();

let finalWeight = arr.map(e => e.weight);
finalWeight = [...new Set(finalWeight)].sort();

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