<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
* {
margin: 0;
padding: 0;
}
.wrapper {
width: 500px;
height: 500px;
border: 1px solid red;
margin: 20px 120px;
position: relative;
}
.small {
width: 100%;
height: 100%;
}
.small img {
width: 100%;
}
.big {
width: 500px;
height: 500px;
border: 2px solid #ddd;
position: absolute;
top: 0;
left: 520px;
overflow: hidden;
display: none;
}
.mask {
width: calc(500 / 800 * 500px);
height: calc(500 / 800 * 500px);
background-color: rgba(255, 255, 40, 0.4);
position: absolute;
top: 0;
left: 0;
cursor: move;
display: none;
}
.big img {
position: absolute;
}
</style>
</head>
<body>
<div class="wrapper">
<div class="small">
<img src="./images/small.jpg" alt="" />
<div class="mask"></div>
</div>
<div class="big">
<img src="./images//big.jpg" alt="" />
</div>
</div>
</body>
<script>
var wrapper = document.querySelector(".wrapper");
var small = document.querySelector(".small");
var mask = document.querySelector(".mask");
var big = document.querySelector(".big");
var bigImg = document.querySelector(".big img");
small.onmouseover = function () {
mask.style.display = "block";
big.style.display = "block";
};
small.onmouseout = function () {
mask.style.display = "none";
big.style.display = "none";
};
small.onmousemove = function (event) {
var e = event || window.event;
var x = e.clientX - wrapper.offsetLeft - mask.offsetWidth / 2;
var y = e.clientY - wrapper.offsetTop - mask.offsetHeight / 2;
var maxX = small.offsetWidth - mask.offsetWidth;
var maxY = small.offsetHeight - mask.offsetHeight;
x = x < 0 ? 0 : x;
y = y < 0 ? 0 : y;
x = x > maxX ? maxX : x;
y = y > maxY ? maxY : y;
mask.style.left = x + "px";
mask.style.top = y + "px";
bigImg.style.left = - (x / small.offsetWidth) * big.offsetWidth + "px";
bigImg.style.top = - (y / small.offsetHeight) * big.offsetHeight + "px";
}
</script>
</html>
