js 实现计时器

使用 setTimeout 实现单次计时器

setTimeout(() => {
  console.log('计时结束');
}, 3000); // 3秒后执行

使用 setInterval 实现循环计时器

let counter = 0;
const timer = setInterval(() => {
  console.log(`已过去 ${++counter} 秒`);
  if (counter >= 5) {
    clearInterval(timer);
  }
}, 1000); // 每秒执行一次

高性能 requestAnimationFrame 计时器

let startTime = null;
function step(timestamp) {
  if (!startTime) startTime = timestamp;
  const elapsed = timestamp - startTime;
  if (elapsed < 3000) { // 运行3秒
    console.log(Math.floor(elapsed / 1000));
    window.requestAnimationFrame(step);
  }
}
window.requestAnimationFrame(step);

精确到毫秒的计时器实现

class PrecisionTimer {
  constructor(duration, callback) {
    this.start = performance.now();
    this.timer = setInterval(() => {
      const elapsed = performance.now() - this.start;
      callback(elapsed);
      if (elapsed >= duration) clearInterval(this.timer);
    }, 16); // 约60fps
  }
}

new PrecisionTimer(5000, (ms) => {
  console.log(`已过去 ${ms.toFixed(2)} 毫秒`);
});

暂停/恢复功能的计时器实现

class PausableTimer {
  constructor(interval, callback) {
    this.remaining = interval;
    this.timerId = null;
    this.start = null;
    this.callback = callback;
  }

  startTimer() {
    this.start = Date.now();
    this.timerId = setTimeout(this.callback, this.remaining);
  }

  pause() {
    clearTimeout(this.timerId);
    this.remaining -= Date.now() - this.start;
  }

  resume() {
    this.startTimer();
  }
}

使用 Web Worker 实现后台计时器

worker.js:

let interval;
self.onmessage = (e) => {
  if (e.data === 'start') {
    let counter = 0;
    interval = setInterval(() => {
      self.postMessage(++counter);
    }, 1000);
  } else if (e.data === 'stop') {
    clearInterval(interval);
  }
};

主线程:

const worker = new Worker('worker.js');
worker.onmessage = (e) => {
  console.log(`Worker计时: ${e.data}秒`);
};
worker.postMessage('start');

// 停止计时
// worker.postMessage('stop');