javascript - js用时间差写一个倒计时怎么实现？

Question

后台给了startTime和endTime的时间戳，通过他俩的差写一个倒计时，求解

Answer 1

没说是vue几就当是vue2了，反正vue3也兼容vue2写法，主要是搞清楚时分秒怎么算
Vue playground

Answer 2

Countdown.vue：

<template>  <span class="countdown">{{ hours }}:{{ minutes }}:{{ seconds }}</span></template><script setup>import { ref, onMounted, onUnmounted } from "vue";// 设置开始时间和结束时间const startTime = new Date("2023-08-01T19:00:00"); // 18:00 pm Aug 1thconst endTime = new Date("2023-08-03T19:00:00"); // 18:00 pm Aug 3th// 计算倒计时的总秒数const countdownTime = Math.floor((endTime - startTime) / 1000);// 结束时间戳const endTimestamp = ref(startTime.getTime() + countdownTime * 1000);const hours = ref("00");const minutes = ref("00");const seconds = ref("00");let intervalId;const updateCountdown = () => {  const remainingTime = endTimestamp.value - Date.now();  if (remainingTime <= 0) {    clearInterval(intervalId);  } else {    hours.value = String(Math.floor(remainingTime / 3600000)).padStart(2, "0");    minutes.value = String(      Math.floor((remainingTime % 3600000) / 60000)    ).padStart(2, "0");    seconds.value = String(Math.floor((remainingTime % 60000) / 1000)).padStart(      2,      "0"    );  }};onMounted(() => {  updateCountdown();  intervalId = setInterval(updateCountdown, 1000);});onUnmounted(() => {  clearInterval(intervalId);});</script>

纯js：

let endTime = new Date("2023-12-31T23:59:59").getTime(); // 你的结束时间let startTime = new Date().getTime(); // 你的开始时间let countdown = setInterval(function() {    let now = new Date().getTime();    let distance = endTime - now;    let hours = Math.floor(distance / (1000 * 60 * 60));    let minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));    let seconds = Math.floor((distance % (1000 * 60)) / 1000);    console.log(hours + "h " + minutes + "m " + seconds + "s ");    if (distance < 0) {        clearInterval(countdown);        console.log("Countdown Finished!");    }}, 1000);