html5的拖拽dragAPI（如果看了API不懂，看看那三个案例就会恍然大悟）

 1 DOCTYPE html>
 2 html>
 3 head lang="en">
 4     meta charset="UTF-8">
 5     title>拖动小熊title>
 6     style>
 7         body{
 8             margin:0;
 9             position: relative;
10         }
11         img{
12             position:absolute;
13             width: 150px;
14             height: 150px;
15         }
16     style>
17 head>
18 body>
19 h3>随着鼠标拖动而移动的小猫咪h3>
20 img id="cat" src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1537438350926&di=d40ad5be9fac73fbcebfcbec85a88739&imgtype=0&src=http%3A%2F%2Fd.hiphotos.baidu.com%2Fzhidao%2Fwh%253D450%252C600%2Fsign%3D88c8f471f9039245a1e0e90bb2a488f4%2F9a504fc2d5628535aedbd09d95ef76c6a7ef6356.jpg" alt=""/>
21 script>
22     var cat = document.getElementById(‘cat‘);
23     cat.ondragstart = function(e){
24         console.log(‘cat开始移动‘);
25         offsetX = e.offsetX;
26         offsetY = e.offsetY;
27     };
28     cat.ondrag = function(e){
29         // console.log(‘事件源cat正在拖动中‘);
30         var x = e.pageX;
31         var y = e.pageY;
32         console.log(x + ‘-‘ +y);
33         if(x === 0 && y === 0){//不处理最后一刻x,y都为0 的情景
34             return
35         };
36         x -= offsetX;
37         y -= offsetY;
38         cat.style.left = x+ ‘px‘;
39         cat.style.top = y + ‘px‘;
40     }
41     cat.ondragend = function (e) {
42         console.jlog(‘cat源对象拖动结束‘)
43     }
44 script>
45 body>
46 html>

 1 DOCTYPE html>
 2 html lang="en">
 3 head>
 4     meta charset="UTF-8">
 5     title>小喵咪喂给大黄鱼title>
 6     style>
 7         body{
 8             text-align: center;
 9         }
10 
11         img{
12             width: 80px;
13             height: 80px;
14             border-radius:100%;
15         }
16         #fish{
17             margin-top: 200px;
18             opacity: .2;
19         }
20     style>
21 head>
22 body>
23  h3>小喵咪拖到大黄鱼上面的时候消失（删除小喵咪）h3>
24  img   class="cat"   id="cat1" src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1537439299088&di=4abcae9fe10a919fd23695be63506d91&imgtype=0&src=http%3A%2F%2Fimg.zcool.cn%2Fcommunity%2F01c2e05777054e0000012e7eceda20.jpg%401280w_1l_2o_100sh.jpg" alt="">
25  img   class="cat"   id="cat2" src="http://img4.imgtn.bdimg.com/it/u=2404190189,262583459&fm=26&gp=0.jpg" alt="">
26  img   class="cat"   id="cat3" src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1537439359473&di=94af89f7165210577af8d9682ca7b90b&imgtype=0&src=http%3A%2F%2Fimg.zcool.cn%2Fcommunity%2F031763d577b43b30000018c1bcaaa23.jpg" alt="">
27  br>
28  img   id="fish"   src="https://ss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=2614718913,3898275106&fm=26&gp=0.jpg" alt="">
29 body>
30 script>
31     //要想从数据库中删除猫咪，就需要猫咪的图片地址是后台传值过来的，然后循环遍历在页面中，当拖动删除的时候，删除掉数据库中的数据即可；然后刷新页面
32     var  cat = document.getElementsByClassName(‘cat‘)//找到所有的猫咪
33     for(var i = 0;icat.length;i++){
34         var catSingle = cat[i];
35         catSingle.ondragstart  = function(e){//循环遍历猫咪，当dragstart拖动开始的时候，setData设置他的id到e.dataTransfer中
36             e.dataTransfer.setData(‘catId‘,this.id);
37         }
38     }
39     fish.ondragenter = function(){//当如到鱼种时候，让鱼的透明度为1；
40         console.log(‘已经拖入‘)
41         fish.style.opacity =‘1‘;
42     }
43     fish.ondragleave = function () {//拖动离开鱼的时候
44         console.log(‘拖动离开‘);
45         fish.style.opacity =‘.2‘;
46     }
47     fish.ondragover = function (e) {//拖动悬浮在鱼上
48         e.preventDefault()
49     }
50     fish.ondrop = function(e){//拖动放开时候；获取拖动开始时候设置的数据；然后从dom结构中移除；
51         console.log(‘放开拖动‘)
52         fish.style.opacity = ‘.2‘
53         var id = e.dataTransfer.getData(‘catId‘)
54         console.log(id)
55         var dragId = document.getElementById(id);
56         dragId.parentNode.removeChild(dragId)
57     }
58 
59 script>
60 html>

 1 DOCTYPE html>
 2 html>
 3 head lang="en">
 4     meta charset="UTF-8">
 5     title>拖动一张图片到浏览器中title>
 6     style>
 7         body{
 8             text-align: center;
 9         }
10         #container {
11             border: 1px solid #aaa;
12             border-radius: 3px;
13             padding: 10px;
14             margin: 10px;
15             min-height: 400px;
16         }
17     style>
18 head>
19 body>
20 
21 h1>拖放API的扩展知识h1>
22 h3>请拖动您的照片到下方方框区域h3>
23 div id="container">div>
24 
25 script>
26     var container = document.getElementById(‘container‘)
27    document.ondragover = function(e){
28        e.preventDefault()
29    }
30    document.ondrop = function(e){
31        e.preventDefault()
32    }
33    container.ondragover = function(e){
34        e.preventDefault()
35    }
36    container.ondrop = function(e){
37         var paper = e.dataTransfer.files[0];
38         var file = new FileReader();
39         file.readAsDataURL(paper)
40        file.onload = function(){
41             console.log(‘读取文件完成‘)
42            console.log(file.result)
43            var img = new Image();
44             img.src =file.result;
45             container.appendChild(img)
46        }
47    }
48 script>
49 body>
50 html>

 1 div.ondrop = function(e){
 2 
 3 var f = e.dataTransfer.files[0];      //找到拖放的文件
 4 
 5 var fr = new FileReader();        //创建文件读取器
 6 
 7 fr.readAsURLData(f);         //读取文件内容
 8 
 9 fr.onload = function(){       //读取完成
10 
11 img.src = fr.result;        //使用读取到的数据
12 
13 }
14 
15  }