C#后端计算下次周三10点，JS前端实现秒杀倒计时

private string GetNextWednesdayTenAM()
{
    // 将当前星期几转为整数索引
    int currentDayIndex = (int)DateTime.Now.DayOfWeek;
    // 周三的索引通常为 3
    int wednesdayIndex = (int)DayOfWeek.Wednesday;
    
    DateTime targetDate;
    
    // 如果今天是周三之前（含周三），目标是本周三
    if (currentDayIndex < wednesdayIndex)
    {
        // 计算距离本周三的偏移量
        DateTime thisWednesday = DateTime.Now.AddDays(wednesdayIndex - currentDayIndex);
        targetDate = new DateTime(thisWednesday.Year, thisWednesday.Month, thisWednesday.Day, 10, 0, 0);
    }
    else
    {
        // 如果今天已过周三，目标是下周周三
        DateTime nextWednesday = DateTime.Now.AddDays(7 + wednesdayIndex - currentDayIndex);
        targetDate = new DateTime(nextWednesday.Year, nextWednesday.Month, nextWednesday.Day, 10, 0, 0);
    }
    
    return targetDate.ToString("yyyy-MM-dd HH:mm:ss");
}

$(document).ready(function() {
    // 使用 everyTime 插件每秒执行一次，也可替换为原生 setInterval
    $('body').everyTime('1s', function() {
        var nowDate = new Date();
        // 获取后端传递的时间字符串，并修复部分浏览器解析 'YYYY-MM-DD' 为 Invalid Date 的问题
        var endDateStr = $("#sp_next").html().replace(/-/g, "/");
        var endDate = new Date(endDateStr);
        
        if (isNaN(endDate.getTime())) return; // 确保日期合法

        // 计算时间差（毫秒）
        var timeold = endDate.getTime() - nowDate.getTime();
        
        // 防止跨天时计算错误，重新整理算法
        var sectimeold = timeold / 1000;
        var secondsold = Math.floor(sectimeold);
        
        var msPerDay = 24 * 60 * 60 * 1000;
        var e_daysold = timeold / msPerDay;
        var daysold = Math.floor(e_daysold);
        
        // 计算剩余的小时数：总小时数 - 完整的天数*24，这里原逻辑略有冗余，优化如下：
        // 更标准的做法是直接按余数计算
        var hours = Math.floor((timeold % msPerDay) / (1000 * 60 * 60));
        var minutes = Math.floor((timeold % (1000 * 60 * 60)) / (1000 * 60));
        var seconds = Math.floor((timeold % (1000 * 60)) / 1000);

        // 补零处理
        hours = hours < 10 ? "0" + hours : hours;
        minutes = minutes < 10 ? "0" + minutes : minutes;
        seconds = seconds < 10 ? "0" + seconds : seconds;

        // 倒计时结束判断
        if (timeold < 0) {
            $(".seckill_time").html("00");
            $(".seckill_minute").html("00");
            $(".seckill_second").html("00");
            // 可选：清除定时器或提示开始
        } else {
            $(".seckill_time").html(hours);
            $(".seckill_minute").html(minutes);
            $(".seckill_second").html(seconds);
        }
    });
});