prefix incrementor vs postfix incrementor is critical for this to work ++prev != prev++

prefix_postfix_incrementors_filter.js

// 7. Write a JavaScript function that accepts a string as a parameter and counts the number of vowels within the string. Go to the editor
// Note : As the letter 'y' can be regarded as both a vowel and a consonant, we do not count 'y' as vowel here. 
// Example string : 'The quick brown fox' 
// Expected Output : 5
((str) => console.log(
  str.split('')
  .reduce( 
    (prev, current) => {
      if("aeiouAEIOU".split('').indexOf(current) != -1){
        return ++prev;
      } else{ 
        return prev
      };
      },0 ) 
  ))("The quick brown fox");
//  NOTE:   prefix incrementor vs postfix incrementor is critical for this to work   ++prev  != prev++