【代码】放大镜效果

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前言

JS实现淘宝商品放大镜效果

源代码

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    .cur {
      position: relative;
      width: 400px;
      height: 400px;
      background: url("img/fire-fox-logo.png");
      background-size: 400px 400px;
    }

    .slider {
      position: absolute;
      width: 100px;
      height: 100px;
      background: black;
      /* 透明度 */
      opacity: 50%;
    }

    .enlarge {
      position: absolute;
      width: 400px;
      height: 400px;
      margin: 0 400px;
      background: url("img/fire-fox-logo.png");
      background-size: 1600px 1600px;
    }

  </style>
</head>
<body>

<div class="cur">
  <div class="slider"></div>
  <div class="enlarge"></div>
</div>

</body>
</html>
<script>

  let cur = document.querySelector(".cur");
  let slider = document.querySelector(".slider");
  let enlarge = document.querySelector(".enlarge");

  slider.onmousedown = function(event) {

    let e = event||window.event;

    let startX = e.offsetX;
    let startY = e.offsetY;

    document.onmousemove = function(event1) {

      let e1 = event1||window.event;

      let l = e1.clientX - startX;
      let t = e1.clientY - startY;

      // console.log(cur.style);

      // 限定拖拽区域
      if (e1.clientX - startX >= 0 && e1.clientX - startX <= 300 && e1.clientY - startY >=0 && e1.clientY - startY <= 300) {

        slider.style.left = l + "px";
        slider.style.top = t + "px";

        // 改变放大镜中的图片位置
        enlarge.style.backgroundPosition= `-${l*4}px -${t*4}px`;

      }

    }

  }

  slider.onmouseup = function() {
    document.onmousemove = null;
  }

</script>

完成

参考文献

哔哩哔哩——web前端小清风