[Codewars] Weight for weight (5 kyu) / JavaScript

https://www.codewars.com/kata/55c6126177c9441a570000cc

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DESCRIPTION:

My friend John and I are members of the "Fat to Fit Club (FFC)". John is worried because each month a list with the weights of members is published and each month he is the last on the list which means he is the heaviest.

I am the one who establishes the list so I told him: "Don't worry any more, I will modify the order of the list". It was decided to attribute a "weight" to numbers. The weight of a number will be from now on the sum of its digits.

For example 99 will have "weight" 18, 100 will have "weight" 1 so in the list 100 will come before 99.

Given a string with the weights of FFC members in normal order can you give this string ordered by "weights" of these numbers?

 

Example:

"56 65 74 100 99 68 86 180 90" ordered by numbers weights becomes: 

"100 180 90 56 65 74 68 86 99"

When two numbers have the same "weight", let us class them as if they were strings (alphabetical ordering) and not numbers:

180 is before 90 since, having the same "weight" (9), it comes before as a string.

All numbers in the list are positive numbers and the list can be empty.

 

Notes

• it may happen that the input string have leading, trailing whitespaces and more than a unique whitespace between two consecutive numbers
• For C: The result is freed.

 

코드

function orderWeight(strng) {
  const arr = [];
  if(!strng.length) return '';
  strng = strng.split(' ').map(Number);
  for(let i = 0; i < strng.length; i++){
    arr.push([strng[i], strng[i].toString().split('').map(Number).reduce((a, b) => a + b, 0)]);
  }
  return arr.sort((a, b) => {
    if(a[1] === b[1]){
      return String(a[0]).localeCompare(String(b[0]));
    } else{
      return a[1] - b[1];
    }
  }).map(el => el[0]).join(' ');
}