大致功能的思路:
1、有一个放原始图片的盒子
2、当鼠标移入这个盒子，在右侧创建一个相同大小的镜像盒子，镜像盒子里创建一个放大4倍的镜像图片，同时也在原始盒子里创建一个放大镜（若存在就display:block，若不存在就创建，镜像盒子同理）
3、当鼠标移动时，原始盒子里的放大镜跟随鼠标移动（类似拖拽功能），镜像盒子里的图片的top和left值是原始盒子里放大镜的top和left值的-4倍
4、当鼠标移出原始盒子时,隐藏镜像盒子和放大镜
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>magnifier</title>
<style>
*{margin: 0px;padding: 0px;}
.imgContent{
width: 420px;
height: 300px;
position: relative;
margin-left: 50px;
margin-top: 50px;
}
.imgContent>img{
width: 420px;
height: 300px;
}
</style>
</head>
<body>
<div class="imgcontent" id="imgContent1">
<img src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1488436622116&di=e3c2b2a5c847d6051d8daaec9a9a2131&imgtype=0&src=http%3A%2F%2F2a.zol-img.com.cn%2Fproduct%2F174_1200x900%2F888%2FceeY9tJ1QRFLk.jpg" alt="iphone7">
</div>
</body>
<script>
function Scaler(id){
var me = this
var originalDiv = document.querySelector("#"+id)
var mirrorDiv = null
var mirrorImg = null
var scaler = null
var real_left = originalDiv.offsetLeft
var real_right = originalDiv.offsetWidth+originalDiv.offsetLeft
var real_top = originalDiv.offsetTop
var real_bottom = originalDiv.offsetHeight+originalDiv.offsetTop
//创建镜像盒子
this.createMirror = function(){
var originalStyle = getComputedStyle(originalDiv)
mirrorDiv = document.createElement("div")
mirrorDiv.style.cssText = 'width:'+originalStyle.width+
';height:'+originalStyle.height+
';position:absolute;left:'+originalStyle.width+
';top:0px;margin-left:10px;overflow:hidden;';
//创建镜像图片
mirrorImg = document.createElement("img")
mirrorImg.style.cssText = 'width:'+(originalDiv.offsetWidth*4)+
'px;height:'+originalDiv.offsetHeight*4+'px;position:absolute;top:0px;left:0px;'
mirrorImg.src = document.querySelector("#"+id+" img").src
mirrorDiv.appendChild(mirrorImg)
originalDiv.appendChild(mirrorDiv)
}
//创建放大镜
this.createScaler = function(left,top){
scaler = document.createElement("div")
scaler.style.cssText = 'width:100px;height:100px;background-color:yellow;opacity:0.4;position:absolute;'
scaler.style.top = top;
scaler.style.left = left;
originalDiv.appendChild(scaler)
}
//设置镜像图片位置
this.setImgPosition = function(left,top){
mirrorImg.style.left = '-'+left+'px'
mirrorImg.style.top = '-'+top+'px'
}
//鼠标移入事件
this.e_mouseover = function(){
originalDiv.style.cursor = "move"
if (!mirrorDiv) {
me.createMirror()
}else{
mirrorDiv.style.display = "block"
};
if (!scaler) {
me.createScaler(0,0)
}else{
scaler.style.display = "block"
};
}
//鼠标移出事件
this.e_mouseleave = function(){
mirrorDiv.style.display = "none"
scaler.style.display = "none"
}
//鼠标移动事件(关键代码)
this.e_mousemove = function(e){
// 判断鼠标是否移出原始盒子
if (e.clientX > real_right || e.clientX < real_left || e.clientY > real_bottom || e.clientY < real_top ) {
me.e_mouseleave()
return false
};
// 鼠标到原始盒子顶部的距离
var padTop = e.clientY-real_top
// 鼠标到原始盒子左侧的距离
var padLeft = e.clientX-real_left
//放大镜跟随鼠标移动(-50是因为让鼠标在放大镜的中心)
scaler.style.top = padTop-50;
scaler.style.left = padLeft-50;
//因为镜像图片放大了4倍，所以跟随移动的时候是4倍
me.setImgPosition((padLeft-50)*4,(padTop-50)*4)
}
//注册事件监听
originalDiv.onmouseover = this.e_mouseover
originalDiv.onmouseleave = this.e_mouseleave
originalDiv.onmousemove = function(e){
me.e_mousemove(e)
}
}
// 创建图片放大功能对象,参数为原始盒子id即可(放大镜大小,镜像图片放大倍数都可设为参数传递)
new Scaler("imgContent1");
</script>
</html>