【总结】JavaScript可以实现的3个有趣小功能

<div class="follow"></div>

.follow {
   ...
   position: fixed;
}

document.addEventListener('mousemove', (event) => {
  const followItem = document.querySelector('.follow');
  followItem.style.left = event.clientX + 'px';
  followItem.style.top = event.clientY + 'px';
})

<div class="slider">
    <img src="./img/1.jpg" />
    <img src="./img/2.jpg" />
    <img src="./img/3.jpg" />
</div>

.slider {
   width: 100%;
   height: 500px;
   overflow: hidden;
  position: relative;
}

setInterval(() => {
   // 定时器要做的事情
}, 2000); // 每2秒执行一次

let index = 0; // 初始值为0
const slider = document.querySelector('.slider');
const imgs = slider.children; // 获取容器内所有img元素
setInterval(() => {
   index++;
   if(index === imgs.length) {
      index = 0;
   }
   const showImg = imgs[index];
   showImg.classList.add('show');
   ... // 隐藏其他图片
}, 2000);

<div class="box">
   <div class="title">更多</div>
   <div class="content" style="display: none">
      ...
   </div>
</div>

.box .title {
   cursor: pointer;
}

const box = document.querySelector('.box');
box.addEventListener('click', () => {
   const content = box.querySelector('.content');
   if(content.style.display === 'none') {
      content.style.display = 'block';
   } else {
      content.style.display = 'none';
   }
});