使用电脑逛淘宝，京东等商城时，将鼠标移入图片中，图片会放大，之前一直在想这种是怎么实现的，前两天刚写出来，纯js实现的，无任何工具库。下面先来看下思路吧！
刚学js的时候可能对于布局不是很重要，但学到面向对象编程后，布局就变得很重要了，有时候布局会影响到整体效果；先来看下布局吧！
1 <div class="photo">
2 <div class="sbox">
3 <img src="http://img0.imgtn.bdimg.com/it/u=4175582523,2707192513&fm=15&gp=0.jpg">
4 <span></span>
5 </div>
6 <div class="bbox">
7 <img src="http://img0.imgtn.bdimg.com/it/u=4175582523,2707192513&fm=15&gp=0.jpg">
8 </div>
9 <div class="nav">
10 <span> <</span>
11 <img src="http://img0.imgtn.bdimg.com/it/u=4175582523,2707192513&fm=15&gp=0.jpg" class="selected">
12 <img src="http://img4.imgtn.bdimg.com/it/u=181188734,374783636&fm=15&gp=0.jpg">
13 <img src="http://img2.imgtn.bdimg.com/it/u=2136674516,3472494802&fm=15&gp=0.jpg">
14 <img src="http://img0.imgtn.bdimg.com/it/u=3344949169,188332301&fm=15&gp=0.jpg">
15 <span>></span>
16 </div>
17 </div>
18
19
20 <style>
21 .photo {
22 width: 98%;
23 height: 500px;
24 margin: 20px auto;
25 border: 1px solid black;
26 position: relative;
27 }
28
29 .sbox {
30 width: 600px;
31 height: 300px;
32 position: absolute;
33 top: 20px;
34 left: 20px;
35 }
36
37 .sbox img {
38 width: 600px;
39 height: 300px;
40 }
41
42 .sbox span {
43 position: absolute;
44 background-color: rgba(199, 199, 199, .5);
45 top: 0;
46 display: none;
47 left: 0;
48 }
49
50 .bbox {
51 width: 600px;
52 height: 300px;
53 overflow: hidden;
54 position: absolute;
55 top: 20px;
56 left: 630px;
57 display: none;
58 }
59
60 .bbox img {
61 width: 1200px;
62 height: 600px;
63 position: absolute;
64 top: 0;
65 left: 0;
66 }
67
68 .nav {
69 width: 300px;
70 height: 32px;
71 position: absolute;
72 overflow: hidden;
73 bottom: 20px;
74 left: 20px;
75
76 }
77
78 .nav img {
79 width: 60px;
80 height: 30px;
81 border: 1px solid #dddddd;
82 }
83
84 .nav img:first-of-type {
85 margin-left: 20px;
86 }
87
88 .nav span {
89 position: absolute;
90 width: 16px;
91 height: 32px;
92 text-align: center;
93 line-height: 30px;
94 background-color: #cccccc;
95 top: 0;
96 cursor: pointer;
97 }
98
99 .nav span:last-child {
100 right: 0;
101 }
102
103 .nav .selected {
104 border: 1px solid #e48c63;
105 }
106 </style>
布局就搞定了，比较简单的哈。下面就是一个思路吧
- 选择元素
- 鼠标进入
- 显示span和大图
- 计算span的宽高
- 鼠标移出
- 隐藏span和大图
- 鼠标移动
- span跟随鼠标移动
- span的边界限定
- 计算比例
- 大图跟随小图移动
大体思路就是这样的，个人建议是根据思路直接自己写，实在不会可以参照我的代码哈！因为自己写出来的和看了别人代码再写出来的感觉不太一样的。好啦，下面就是js部分的代码！
1 <script>
2 // 创建函数
3 function big() {
4 // 获取元素
5 this.span = document.queryselector(".sbox span");
6 this.sbox = document.queryselector(".sbox");
7 this.bbox = document.queryselector(".bbox");
8 this.simg = document.queryselector(".sbox img");
9 this.bimg = document.queryselector(".bbox img");
10 this.img = document.queryselectorall(".nav img");
11 this.init();
12 }
13 big.prototype.init = function () {
14 // this的指向问题
15 var that = this;
16 for (var i = 0; i < this.img.length; i++) {
17 this.img[i].index = i;
18 // 点击导航图
19 this.img[i].onclick = function () {
20 for (var j = 0; j < that.img.length; j++) {
21 // 清除默认样式
22 that.img[j].classname = "";
23 }
24 // 给当前的图片加样式
25 that.img[this.index].classname = "selected";
26 that.index = this.index;
27 // 将当前图放入主体框中
28 that.changeimg();
29 }
30 }
31 // 鼠标移入事件
32 this.sbox.onmouseover = function () {
33 // 显示
34 that.span.style.display = "block";
35 that.bbox.style.display = "block";
36 // 计算span宽高
37 that.span.style.width = that.bbox.offsetwidth / that.bimg.offsetwidth * that.sbox.offsetwidth + "px";
38 that.span.style.height = that.bbox.offsetheight / that.bimg.offsetheight * that.sbox.offsetheight + "px";
39 }
40 // 鼠标移动
41 this.sbox.onmousemove = function () {
42 that.move();
43 }
44 // 鼠标移出
45 this.sbox.onmouseout = function () {
46 // 隐藏
47 that.span.style.display = "none";
48 that.bbox.style.display = "none";
49 }
50 }
51 // 改变图片
52 big.prototype.changeimg = function () {
53 this.simg.src = this.img[this.index].src;
54 this.bimg.src = this.img[this.index].src;
55 }
56 // 移动
57 big.prototype.move = function () {
58 this.span.style.left = event.clientx - this.sbox.offsetleft - this.span.offsetwidth / 2 + "px";
59 this.span.style.top = event.clienty - this.sbox.offsettop - this.span.offsetheight / 2 + "px";
60 // 边界限定
61 if (this.span.offsetleft < 0) {
62 this.span.style.left = 0;
63 }
64 if (this.span.offsettop < 0) {
65 this.span.style.top = 0;
66 }
67 if (this.span.offsetleft > this.sbox.offsetwidth - this.span.offsetwidth) {
68 this.span.style.left = this.sbox.offsetwidth - this.span.offsetwidth + "px";
69 }
70 if (this.span.offsettop > this.sbox.offsetheight - this.span.offsetheight) {
71 this.span.style.top = this.sbox.offsetheight - this.span.offsetheight + "px";
72 }
73 // 计算比例
74 var num=this.bbox.offsetwidth/this.bimg.offsetwidth;
75 console.log(num);
76 // 大图移动
77 this.bimg.style.left=-(this.span.offsetleft/num)+"px";
78 this.bimg.style.top=-(this.span.offsettop/num)+"px";
79 }
80 new big();
81 </script>
仅供参考，如有疑问，欢迎评论哈！
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