要计算字符串中字符出现的次数，请尝试运行以下代码-
<!DOCTYPE html>
<html>
<body>
<script>
function displayCount() {
setTimeout(function() {
var str = document.getElementById('str1').value;
var letter = document.getElementById('letter1').value;
letter = letter[letter.length-1];
var lCount;
for (var i = lCount = 0; i < str.length; lCount += (str[i++] == letter));
document.querySelector('p').innerText = lCount;
return lCount;
}, 50);
}
</script>
Enter String: <input type="text" id="str1"><br><br>
Enter Letter: <input onkeypress="displayCount()" type="text" id="letter1"><br><br>
<button onclick="displayCount()">Click for Result</button><br><br>
result= <p></p>
</body>
</html>