前端倒计时与定时任务实现技巧

function startCountdown(targetDate) {
  const timer = setInterval(() => {
    const now = new Date().getTime();
    const distance = targetDate - now;
if (distance < 0) {
  clearInterval(timer);
  document.getElementById("countdown").innerHTML = "倒计时结束！";
  return;
}

const days = Math.floor(distance / (1000 * 60 * 60 * 24));
const hours = Math.floor((distance % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));
const minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));
const seconds = Math.floor((distance % (1000 * 60)) / 1000);

document.getElementById("countdown").innerHTML =
  `${days}天 ${hours}小时 ${minutes}分 ${seconds}秒`;
}, 1000);
}
// 使用示例
const target = new Date("2025-12-31T00:00:00").getTime();
startCountdown(target);

const pollTask = setInterval(async () => {
  try {
    const res = await fetch("/api/status");
    const data = await res.json();
    console.log("当前状态:", data.status);
    // 更新UI
    document.getElementById("status").textContent = data.status;
  } catch (err) {
    console.error("请求失败", err);
  }
}, 5000); // 每5秒执行一次

let timerId;
function start() {
timerId = setInterval(() => {
console.log("执行中...");
}, 1000);
}
function stop() {
clearInterval(timerId);
console.log("定时器已停止");
}