JS代码修改：限制输入字符为数字、下划线和大小写字母，最大长度255字符

<script>
function checkWeight() {
    var maxAttempts = 10; 
    var today = new Date();
    today.setHours(0, 0, 0, 0); 
    var expires = new Date(today.getTime() + (24 * 60 * 60 * 1000)); 

    var attempts = getCookie('attempts'); 
    if (attempts === null) {
        attempts = 0;
    }
    if (attempts >= maxAttempts) {
        alert('免费用户只能查询' + maxAttempts + '次，请明天再来，或者找管理员赞助吧');
        return;
    }

    var url = document.getElementById('input-link').value.trim();
    var pattern = /^[a-zA-Z0-9_]{1,255}$/;
    var match = url.match(pattern);
    if (match !== null) {
        var newUrl = 'dy.php?url=' + match[0];
        location.href = newUrl;
        setCookie('attempts', ++attempts, expires); 
    } else {
        alert('输入的链接格式不正确，请重新输入。');
    }
}

function getCookie(name) {
    var pattern = new RegExp('(?:(?:^|.*;)\s*' + name + '\s*\=\s*([^;]*).*$)|^.*$');
    return decodeURIComponent(document.cookie.replace(pattern, '$1')) || null;
}

function setCookie(name, value, expires) {
    document.cookie = name + '=' + encodeURIComponent(value) + '; expires=' + expires.toUTCString() + '; path=/';
}
</script>