正则表达式可以匹配元音，然后可以检查匹配数。

const input = document.querySelector('#vText');
const button = document.querySelector('#vSubBtn');
const output = document.querySelector('#vOutput');

button.onclick = () => {
    const inputText = input.value;
    const vowelCount = (inputText.match(/[aeiou]/gi) ?? []).length;
    output.textContent = `Your text ${inputText} contains ${vowelCount} vowel sounds`;
}

<div id="vHead">
    <h1>VOUT</h1>
    <p>Check a word for vowel sounds</p>
    <input id="vText" type="text" placeholder="Eg: Victor" value="Victor" required>
    <input id="vSubBtn" type="button" value="Check">
</div>
<div id="vOutput"></div>

字符串在js中是可编辑的，因此您可以使用spread操作符获取字符数组并检查它是否为 vowel 或者如果它在 vowel 使用includes方法的数组

//Selecting document element
const voutText = document.querySelector('#vText');
const voutBtn = document.querySelector('#vSubBtn');
const voutBox = document.querySelector('#vOutput');

let vowelCount = 0;

const voutApp = () => {
  const text = voutText.value;
  const vowel = ['A', 'E', 'I', 'O', 'U'];
  [...text].forEach(ch => vowel.includes(ch.toUpperCase()) ? vowelCount++ : "")
  voutBox.innerHTML = `Your text ${vowelCount} contains vowel sounds`; //I have to figure out how to get the vowel counts EG: Your text (Input Value) contains 6 vowels.
}

voutBtn.addEventListener('click', voutApp);

<div id="vHead">
  <h1>VOUT</h1>
  <p>Check a word for vowel sounds</p>
  <input id="vText" type="text" placeholder="Eg: Victor" required>
  <input id="vSubBtn" type="button" value="Check">
</div>
<div id="vOutput"></div>

其他一些帖子展示了如何缩短代码以实现这一目标。如果你想保持你所写的风格，比如使用 for 循环和 alert s等，然后您可以这样做：

//Selecting document element
const voutText = document.querySelector('#vText');
const voutBtn = document.querySelector('#vSubBtn');
const voutBox = document.querySelector('#vOutput');

const voutApp = () => {
    const vowel = ['A', 'E', 'I', 'O', 'U'];
    const voutTextView = voutText.value.toUpperCase();

    let vowelCount = 0;
    for (i = 0; i < voutTextView.length; i++) {
        if (vowel.includes(voutTextView[i])) {
            // This would alert whenever it finds a vowel - even multiple of the same
            alert("Yey! we found vowels, your text contains the vowel sound " + voutTextView[i]);
            vowelCount++;
        }
    }

    if (vowelCount > 0) {
        voutBox.innerHTML = "The passage contains " + vowelCount + " vowel sounds";
    } else {
        voutBox.innerHTML = "Your text contains no vowel sound";
    }
}

voutBtn.addEventListener('click', voutApp);

检查这个

function voutApp(){
  const voutText = document.getElementById('vText');
  const voutBox = document.getElementById('vOutput');
  const vowel = ['A','E', 'I', 'O', 'U'];
  let vowelCount = 0;
  let val = voutText.value;
  let msg1 = 'Yey! we found';
  let vfound = []; 
    for (let i=0; i<val.length; i++) {
        let curChar = val[i].toUpperCase();
        if( vowel.indexOf(curChar) !== -1 ){
          vowelCount += 1;
          vfound.push(curChar);
        }
    }
  if( vowelCount > 0 ){
     voutBox.innerHTML = msg1+' '+vowelCount+' vowels. your text contains the vowel sound '+vfound;
  }else{
    voutBox.innerHTML = 'Your text contains no vowel sound';
  }
}

<div id="vHead">
    <h1>VOUT</h1>
    <p>Check a word for vowel sounds</p>
    <input id="vText" type="text" placeholder="Eg: Victor" value="Victor" required>
    <input id="vSubBtn" type="button" value="Check" onclick="voutApp()">
</div>
<div id="vOutput"></div>