The Most Powerful Word JS

function theMostPowerfulWord(input) {
    let index = 0;
    let word = input[index];
    index++;

    let wordPower = 0;
    let theMostPowerful = "";
    let theBestPower = 0;
    while (word !== "End of words") {

        let wordValue = 0;
        let firstLetter = "";
        for (let i = 0; i < word.length; i++) {

            let letterValue = word.charCodeAt(i);
            wordValue += letterValue;
        }
            firstLetter = word.charAt(0);

            if (firstLetter === "a" || firstLetter === "e" || firstLetter === "i"
            || firstLetter === "o" || firstLetter === "u" || firstLetter === "y"
            || firstLetter === "A" || firstLetter === "E" || firstLetter === "I"
            || firstLetter === "O" || firstLetter === "U" || firstLetter === "Y") {
                wordPower = Math.floor(wordValue * word.length);
            } else {
                wordPower = Math.floor(wordValue / word.length);
            }
            if (wordPower >= theBestPower) {
                theMostPowerful = word;
                theBestPower = wordPower;
            }
            word = input[index];
            index++;
    }
    console.log(`The most powerful word is ${theMostPowerful} - ${theBestPower}`)
}