js实现等待几秒

使用 setTimeout 实现延迟执行

setTimeout(() => {
  console.log('这段代码将在3秒后执行');
}, 3000);

结合 Promise 实现等待

function wait(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function delayedAction() {
  console.log('开始等待');
  await wait(2000);
  console.log('2秒后执行');
}
delayedAction();

使用 async/await 实现顺序等待

async function sequentialWaits() {
  console.log('第一步');
  await new Promise(resolve => setTimeout(resolve, 1000));

  console.log('1秒后执行第二步');
  await new Promise(resolve => setTimeout(resolve, 1500));

  console.log('再1.5秒后执行第三步');
}
sequentialWaits();

循环定时执行

let counter = 0;
const intervalId = setInterval(() => {
  console.log(`每秒执行一次，当前第${++counter}次`);
  if(counter >= 5) clearInterval(intervalId);
}, 1000);

使用 requestAnimationFrame 实现精确等待

function waitFrames(frames) {
  let count = 0;
  return new Promise(resolve => {
    function loop() {
      if(++count >= frames) resolve();
      else requestAnimationFrame(loop);
    }
    requestAnimationFrame(loop);
  });
}

// 假设60fps，等待1秒(60帧)
waitFrames(60).then(() => console.log('1秒后执行'));