<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
*{
margin:0;
padding:0;
}
#box{
width: 350px;
height: 350px;
border:1px solid #ccc;
position: relative;
margin:100px;
}
#small{
position: relative;
}
#mask{
width: 100px;
height: 100px;
position: absolute;
top:0;
left:0;
background: rgba(255,255,0,.4);
cursor: move;
display: none;
}
#big{
width: 450px;
height: 450px;
position: absolute;
top:0;
left: 360px;
overflow: hidden;
display: none;
}
#big img{
position: absolute;
top:0;
left:0;
}
</style>
</head>
<body>
<div id="box">
<div id="small">
<div id="mask"></div>
</div>
<div id="big">
</div>
</div>
<script>
// 獲取元素
var box = document.getElementById("box");
var small = document.getElementById("small");
var mask = document.getElementById("mask");
var big = document.getElementById("big");
var bigImg = big.querySelector("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;
// 獲取鼠標(biāo)位置（可視區(qū)域）
var mX = e.clientX;
var mY = e.clientY;
// 計算放大鏡的移動范圍
var maxLeft = box.offsetWidth - mask.offsetWidth;
var maxTop = box.offsetHeight - mask.offsetHeight;
// 設(shè)置臨時位置
var tempLeft = mX - box.offsetLeft - mask.offsetWidth / 2;
var tempTop = mY - box.offsetTop - mask.offsetHeight / 2;
// 設(shè)置最終位置
var nowLeft = 0;
var nowTop = 0;
if(tempLeft >= maxLeft){
nowLeft = maxLeft;
}else if(tempLeft>0 && tempLeft < maxLeft){
nowLeft = tempLeft;
}
if(tempTop >= maxTop){
nowTop = maxTop;
}else if(tempTop > 0 && tempTop < maxTop){
nowTop = tempTop;
}
// 遮罩跟隨鼠標(biāo)
mask.style.left = nowLeft + "px";
mask.style.top = nowTop + "px";
// 計算移動比例
var ratioX = box.offsetWidth / bigImg.offsetWidth;
var ratioY = box.offsetHeight / bigImg.offsetHeight;
// 大圖位置
bigImg.style.left = - nowLeft / ratioX + "px";
bigImg.style.top = - nowTop / ratioY + "px";
}
</script>
</body>
</html>
這種布局方式相對來說更好操作，小圖和大圖在同一個盒子里浊闪；
難點在于獲取鼠標(biāo)在盒子中的位置恼布，不明白的朋友可以自己畫圖，可以更直觀的理解搁宾。
再一點就是遮罩移動折汞，大圖移動，強調(diào)下盖腿，移動的不是大圖的父級盒子爽待，而是圖片本身，根據(jù)圖片比例移動翩腐，比如鸟款，遮罩在小圖上移動1px，那么在大盒子上移動的就是 1 / 小圖 / 大圖 茂卦。代碼中有所體現(xiàn)何什，如有哪里不清楚，請在下方留言等龙，我會第一時間回復(fù)富俄！
