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js 实现菜单下滑

2026-02-02 15:21:48JavaScript

实现菜单下滑效果

使用JavaScript实现菜单下滑效果通常需要结合CSS过渡或动画。以下是几种常见实现方式：

基础CSS过渡实现

通过添加/移除类名触发CSS过渡效果：

.menu {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease-out;
}

.menu.open {
  max-height: 500px; /* 大于实际内容高度即可 */
}

const menu = document.querySelector('.menu');
const toggleBtn = document.querySelector('.toggle-btn');

toggleBtn.addEventListener('click', () => {
  menu.classList.toggle('open');
});

动态计算高度实现

精确计算内容高度实现平滑过渡：

function toggleMenu() {
  const menu = document.querySelector('.menu');
  if (menu.style.maxHeight) {
    menu.style.maxHeight = null;
  } else {
    menu.style.maxHeight = menu.scrollHeight + 'px';
  }
}

使用Web Animation API

现代浏览器支持的动画API：

const menu = document.querySelector('.menu');

function animateMenu() {
  const isOpen = menu.classList.contains('open');

  const animation = menu.animate([
    { maxHeight: '0px', opacity: 0 },
    { maxHeight: `${menu.scrollHeight}px`, opacity: 1 }
  ], {
    duration: 300,
    easing: 'ease-in-out'
  });

  animation.onfinish = () => {
    menu.classList.toggle('open', !isOpen);
  };
}

带缓动函数的实现

添加更复杂的缓动效果：

function slideMenu(menu, duration = 300) {
  const start = performance.now();
  const startHeight = menu.offsetHeight;
  const endHeight = menu.classList.contains('open') ? 0 : menu.scrollHeight;

  function step(timestamp) {
    const progress = Math.min((timestamp - start) / duration, 1);
    const easeProgress = easeOutQuad(progress);
    menu.style.height = startHeight + (endHeight - startHeight) * easeProgress + 'px';

    if (progress < 1) {
      requestAnimationFrame(step);
    } else {
      menu.classList.toggle('open');
      menu.style.height = '';
    }
  }

  requestAnimationFrame(step);
}

function easeOutQuad(t) {
  return t * (2 - t);
}