Create Object of Arrays from multidimensional Array arranged by key types

Question

Following one of the answers of How to count certain elements in array? created the JavaScript code below to build a Object, what can be used to build a Object named chars what can be used as chars.str and chars.num:

    const arr="abrakadabra".split('');
    const counts = {};
    arr.forEach((el) => {
      counts[el] = counts[el] ? (counts[el] += 1) : 1;
    });
    const countsSorted = Object.entries(counts).sort(([_, b], [__, a]) => a - b);
    console.log(countsSorted); // [["a",5],["b",2],["r",2],["k",1],["d",1]]

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What is the elegant way to create Object from countsSorted what can be used as chars.str and chars.num, like:

Object {
  num: [5, 2, 2, 1, 1],
  str: ["a", "b", "r", "k", "d"]
}

score 0 · Answer 1 · answered Oct 06 '20 at 01:16

With the help of JavaScript Array of Objects Tutorial I was able to understand more and have found the JavaScript Array forEach() Method as a solution. Working example below:

    const arr="abrakadabra".split('');
    const counts = {};
    arr.forEach((el) => {
      counts[el] = counts[el] ? (counts[el] += 1) : 1;
    });
    const countsSorted = Object.entries(counts).sort(([_, b], [__, a]) => a - b);

    var chars = new Object();
    chars.str = [];
    chars.num = [];
    
    countsSorted.forEach((asd) => {
      chars.str.push(asd[0]);
      chars.num.push(asd[1]);
    });

    console.log(chars); // {"str":["a","b","r","k","d"],"num":[5,2,2,1,1]}

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score 0 · Answer 2 · answered Oct 06 '20 at 01:28

You can use Array.reduce() to transform arrays to objects:

const str = "abrakadabra";

const countsSorted = Object.entries(
  str .split('').reduce((acc, el) => {
    acc[el] = (acc[el] ?? 0) + 1;

    return acc;
  }, {})
).sort(([, a], [, b]) => b - a);

const chars = countsSorted.reduce((acc, [str, num]) => {
  acc.str.push(str);
  acc.num.push(num);

  return acc;
}, { str: [], num: [] });

console.log(chars); // {"str":["a","b","r","k","d"],"num":[5,2,2,1,1]}

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Create Object of Arrays from multidimensional Array arranged by key types

2 Answers2