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js秒表实现

2026-02-01 04:20:28JavaScript

实现 JavaScript 秒表

基本 HTML 结构

创建一个简单的 HTML 结构，包含显示时间和控制按钮：

<div id="stopwatch">
  <div id="display">00:00:00</div>
  <button id="startBtn">开始</button>
  <button id="stopBtn">停止</button>
  <button id="resetBtn">重置</button>
</div>

CSS 样式（可选）

添加基本样式美化秒表：

#stopwatch {
  text-align: center;
  font-family: Arial, sans-serif;
}
#display {
  font-size: 2em;
  margin: 20px;
}
button {
  padding: 10px 20px;
  margin: 5px;
  font-size: 1em;
}

JavaScript 核心逻辑

实现秒表功能的核心代码：

let startTime;
let elapsedTime = 0;
let timerInterval;

function formatTime(time) {
  let hours = Math.floor(time / 3600000);
  let minutes = Math.floor((time % 3600000) / 60000);
  let seconds = Math.floor((time % 60000) / 1000);
  let milliseconds = Math.floor(time % 1000);

  return (
    String(hours).padStart(2, "0") + ":" +
    String(minutes).padStart(2, "0") + ":" +
    String(seconds).padStart(2, "0") + "." +
    String(milliseconds).padStart(3, "0").slice(0, 2)
  );
}

function startTimer() {
  startTime = Date.now() - elapsedTime;
  timerInterval = setInterval(function() {
    elapsedTime = Date.now() - startTime;
    document.getElementById("display").textContent = formatTime(elapsedTime);
  }, 10);
}

function stopTimer() {
  clearInterval(timerInterval);
}

function resetTimer() {
  clearInterval(timerInterval);
  elapsedTime = 0;
  document.getElementById("display").textContent = "00:00:00.00";
}

document.getElementById("startBtn").addEventListener("click", startTimer);
document.getElementById("stopBtn").addEventListener("click", stopTimer);
document.getElementById("resetBtn").addEventListener("click", resetTimer);

高级功能扩展

添加计次功能：

let lapTimes = [];
const lapList = document.createElement("ol");
document.getElementById("stopwatch").appendChild(lapList);

function recordLap() {
  lapTimes.push(formatTime(elapsedTime));
  const lapItem = document.createElement("li");
  lapItem.textContent = lapTimes[lapTimes.length - 1];
  lapList.appendChild(lapItem);
}

// 添加计次按钮到HTML
const lapBtn = document.createElement("button");
lapBtn.textContent = "计次";
lapBtn.id = "lapBtn";
document.getElementById("stopwatch").appendChild(lapBtn);
document.getElementById("lapBtn").addEventListener("click", recordLap);

性能优化建议

使用 requestAnimationFrame 替代 setInterval：

function startTimer() {
  startTime = Date.now() - elapsedTime;
  function updateTimer() {
    elapsedTime = Date.now() - startTime;
    document.getElementById("display").textContent = formatTime(elapsedTime);
    timerInterval = requestAnimationFrame(updateTimer);
  }
  timerInterval = requestAnimationFrame(updateTimer);
}

function stopTimer() {
  cancelAnimationFrame(timerInterval);
}