JavaScript Program to find if a number is palindrome or not

Program

<!DOCTYPE html>
<html>
<head>
    <title>Check Palindrome</title>
</head>
<script>
    function palindrome() {
        var str = document.getElementById("actualString").value;
        var revStr = "";
        for (var i = str.length; i >= 0; i--) {
            revStr = revStr + str.charAt(i);
        }
        document.getElementById("reversedNumber").innerHTML = revStr;
        if (str == revStr)
            document.getElementById("palindromeResult").innerHTML = "Palindrome";
        else
            document.getElementById("palindromeResult").innerHTML = "Not Palindrome";
    }
</script>
<body>
    <input type="text" id="actualString" name="actualString">
    <button type="submit" onclick="palindrome()">Check Palindrome</button>
    <p id="reversedNumber"></p>
    <p id="palindromeResult"></p>
</body>
</html>

Output

<p class="output">Check Palindrome</p>
<input type="text" id="actualString" name="actualString">
<button type="submit" onclick="palindrome()">Check Palindrome</button>
<p id="reversedNumber"></p>
<p id="palindromeResult"></p>
<script>
function palindrome() {
    var str = document.getElementById("actualString").value;
    var revStr = "";
    for (var i = str.length; i >= 0; i--) {
        revStr = revStr + str.charAt(i);
    }
    document.getElementById("reversedNumber").innerHTML = revStr;
    if (str == revStr)
        document.getElementById("palindromeResult").innerHTML = "Palindrome";
    else
        document.getElementById("palindromeResult").innerHTML = "Not Palindrome";
}
</script>