知识点，需熟悉下面属性及含义：
offsetLeft //获取元素相对左侧的距离 （计算是从最左侧边框外开始）
offsetTop //获取元素相对顶部的距离 （计算是从最顶部边框外开始）
offsetWidth //获取元素宽度 （border + padding + margin）
offsetHeight //获取元素高度 （border +padding + margin）
clientLeft //测量的是元素左侧边框的宽度
clientHeight //测量的是元素的上边框的宽度
clientWidht //获取元素的宽度 不带边框（padding + margin）
clientHeight //获取元素的高度 不带边框 （padding + margin）
第一种： 商品类
正文：现在很多pc端商城网站详情页面都使用的有放大镜效果，那我们怎样使用一张图片实现放大镜效果呢？具体代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
*{
margin: 0;
padding: 0;
}
#smallImg{
width: 300px;
height: 300px;
position: relative;
}
#smallImg img{
width: 300px;
height: 300px;
}
#lay{
position: absolute;
left: 0;
top: 0;
border: 1px solid #666;
opacity: 0.6;
filter: alpha(opacity = 60);
background: #fff;
display: none;
cursor: move;
}
#bigImg{
width: 300px;
height: 300px;
position: absolute;
left: 320px;
overflow: hidden;
top: 0;
display: none;
}
#bigImg img{
position: absolute;
left: 0;
top: 0;
}
</style>
</head>
<body>
<div id="smallImg">
<img src="img/1.jpg" alt="">
<div id="lay"></div>
</div>
<div id="bigImg">
<img src="img/1.jpg" alt="">
</div>
<script>
window.onload = function(){
var lay = getId("lay"),
smallImg = getId("smallImg"),
bigImg = getId("bigImg");
var imgB = bigImg.children[0]; //大图中的图片
var scale = 4; //缩放倍数 可调整
var w = smallImg.offsetWidth; //小图的宽高
var h = smallImg.offsetHeight;
lay.style.width = w / scale + "px";
lay.style.height = h / scale + "px"; imgB.style.width = w * scale + "px";
imgB.style.height = h * scale + "px";
smallImg.onmouseover = function(){
lay.style.display = "block";
bigImg.style.display = "block";
}
smallImg.onmouseout = function(){
lay.style.display = "none";
bigImg.style.display = "none";
}
smallImg.onmousemove = function(e){
e = e || window.event;
var x = e.clientX - lay.offsetWidth/2;
var y = e.clientY - lay.offsetHeight/2;
if(x <= 0){ //左侧边界判断
x = 0;
}
if(y <= 0){ //顶部边界判断
y = 0;
}
if(x >= smallImg.offsetWidth - lay.offsetWidth ){
x = smallImg.offsetWidth - lay.offsetWidth //右侧边界判断
}
if(y >= smallImg.offsetHeight - lay.offsetHeight ){
y = smallImg.offsetHeight - lay.offsetHeight //底部边界判断
}
lay.style.left = x + "px";
lay.style.top = y + "px";
imgB.style.left = -x*scale + "px"; //图片默认位置为0 0左上角位置 需要反向才能两者相对显示
imgB.style.top = -y*scale + "px";
}
}
function getId(id){
return document.getElementById(id);
}
</script>
</body>
</html>
好了商品外部放大镜效果就这样完成了，而且还带有边界检测。希望可以给有需要的人提供到帮助。
模拟效果图如下：
第二种： 商品内部实现放大效果
<!DOCTYPE html>
<html>
<head>
<title>测试放大镜</title>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
#small_Box{
width: 300px;
height: 300px;
position: relative;
margin: 50px auto;
}
#small_Box img{
width: 100%;
height: 100%;
}
</style>
</head>
<body>
<div id="small_Box"><img src="1.jpg"></div>
<script type="text/javascript">
window.onload = function() {
var span = document.createElement("span");
var box = document.getElementById("small_Box");
var img = document.createElement("img");
var boxWidth = box.clientWidth;
var boxHeight = box.clientHeight;
var scale = 2;
span.style.position = "absolute";
span.style.width = boxWidth / scale+"px";
span.style.height = boxHeight / scale+"px";
span.style.display = 'none';
span.style.overflow = 'hidden';
span.style.backgroundColor = "rgba(255, 255, 255, 0.5)";
span.style.cursor = 'pointer';
box.appendChild(span);
img.setAttribute("src", "1.jpg");
img.style.width = scale*boxWidth + "px";
img.style.height = scale*boxHeight + "px";
box.onmouseover = function(e){
span.style.display = "block";
}
box.onmousemove = function(e){
e = e || window.event;
var x = e.clientX - span.clientWidth / scale - this.offsetLeft;
var y = e.clientY - span.clientHeight / scale - this.offsetTop;
if (x <= 0){
x = 0
}
if (x >= box.clientWidth - span.clientWidth){
x = box.clientWidth - span.clientWidth
}
if (y <= 0){
y = 0
}
if (y >= box.clientHeight - span.clientHeight){
y = box.clientHeight - span.clientHeight
}
span.style.left = x + "px";
span.style.top = y + "px"; img.style.marginLeft = -1 * span.offsetLeft * scale - x + "px";
img.style.marginTop = -1 * span.offsetTop * scale - y + "px";
span.appendChild(img);
} box.onmouseout = function(e){
span.style.display = "none";
}
}
</script>
</body>
</html>
好了商品内部放大镜效果就这样完成了，而且还带有边界检测。希望可以给有需要的人提供到帮助。
模拟效果图如下：
