Get Vowels from String, Sort and return by Count

vowel-sort.js

    var test = "SAMPLE";

    function solution(S) {
    let stringArr = [...S.toLowerCase()];
    let vowelArr = ['a','e','i','o','u'];
    const vowelString = stringArr.filter(letter => vowelArr.includes(letter)).sort().join('');
    let finalString = '';

      vowelArr = vowelArr.map(vowel => { 
        return {
          'vowel': vowel, 
          count: vowelString.split(vowel).length - 1
        }
      }).sort((a, b) => (a.count > b.count) ? -1 : 1)

      // Check for ties
      const highestCount = vowelArr[0].count;
      const tiedVowels = vowelArr.filter(vowel => vowel.count === highestCount); 

      if (tiedVowels.length > 1) {
        const sortedVowels = tiedVowels.sort((a, b) => (a.vowel > b.vowel) ? -1 : 1);

        for (let i = 0; i < sortedVowels.length; i++) {
          const plural = vowelArr[i].count > 1 ? 's' : '';
          const newLine = (sortedVowels.length - 1 !== i) ? '\n' : '';
          finalString = `${finalString}${vowelArr[i].vowel} appears ${vowelArr[i].count} time${plural}${newLine}`;
        }
      } else {
        const plural = vowelArr[0].count > 1 ? 's' : '';
        finalString = `${vowelArr[0].vowel} appears ${vowelArr[0].count} time${plural}`;
      }

      return finalString;
    }    
    

console.log(solution(test));