使用JavaScript实现简单图像放大镜效果

<div class="container">
     
</div>

body,
html {
  height: 100%;
  width: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  overflow: hidden;
  position: relative;
  min-width: 700px;
  background: rgb(202, 201, 201);
}
.container {
  width: 650px;
  height: 400px;
  background: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 5px solid rgb(244, 254, 255);
}

<div id="zoom">
  <img src="https://img-blog.csdnimg.cn/c43ca410ce4a40e4836664f7dbe98ad5.png" alt="">
</div>

#zoom img{
  width: 650px;
  height: 400px;
}

#lens {
  position: absolute;
  border: 2px solid grey;
  border-radius: 50%;
  overflow: hidden;
  cursor: none;
  box-shadow: inset 0 0 10px 2px grey;
  filter: drop-shadow(0 0 2px grey);
}

#lens > * {
  cursor: none;
}

//lensSize => 宽度和高度
const lensSize = 200;

function magnify(id, zoom){
  const el = document.getElementById(id);
//cloneNode() 方法创建一个节点的副本，并返回克隆
  const copy = el.cloneNode(true);
//createElement() 方法创建由 tagName 指定的 HTML 元素
  const lens = document.createElement("div");
  
//setAttribute() 设置指定元素的属性值
  lens.setAttribute("id","lens")  
  lens.style.width = lensSize + "px";
  lens.style.height = lensSize + "px";
  
//appendChild() 方法用于插入一个新节点
  el.appendChild(lens);
//getBoundingClientRect() 方法返回元素的大小及其位置
  el.getBoundingClientRect();
  copy.style.zoom = zoom;
  lens.appendChild(copy);
  
  copy.style.width = (el.offsetWidth * zoom) + "px";
  copy.style.heigth = (el.offsetHeight * zoom) + "px";
  copy.style.position = "absolute";
  
//当指针在元素上移动时执行 MouseMove
  el.addEventListener("mousemove", (ev) => {
//preventDefault() 方法停止选定元素的默认操作
    ev.preventDefault();
    ev.stopPropagation();
    const pos = getCursorPos(ev);
    lens.style.left =  - (lensSize/2) + pos.x + "px";
    lens.style.top = - (lensSize/2) + pos.y + "px";
    copy.style.left = - (pos.x - el.offsetLeft) + (lensSize/zoom)*0.5 + "px";
    copy.style.top = - (pos.y - el.offsetTop) + (lensSize/zoom)*0.5  + "px";
  })
}

  function getCursorPos(e) {
    var x = (window.Event) ? e.pageX : event.clientX + (document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft);
    var y = (window.Event) ? e.pageY : event.clientY + (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop);
    return {x : x , y : y};
  }
//放大值
magnify("zoom", 4)