原生JS实现图片上传并预览功能

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>原生实现图片预览功能</title>
 8 </head>
 9 <body>
10     <label for="file">点击上传文件</label>
11     <input id="file" onchange="uploadFiles()" accept="image/png,image/jpeg" type='file' multiple />
12     <div class="preview">
13         <p>No files currently selected for upload</p>
14     </div>
15     <script>
16         const input = document.querySelector('input');
17         input.style.opacity = 0;
18         function uploadFiles() {
19             const files = input.files; // 从元素的files属性获取文件列表
20             const preview = document.querySelector('.preview');
21             while(preview.firstChild) { // 每次都清空原有列表
22                 preview.removeChild(preview.firstChild);
23             }
24             const ol = document.createElement('ol');
25             preview.appendChild(ol);
26             for(let file of files) {
27                 const li = document.createElement('li');
28                 const newLi = showFiles(file, li, preview);
29                 preview.appendChild(newLi);
30             }
31         }
32         function showFiles(file, li) {
33             const { name, size, type  } = file;
34             const isValidate = validateFileType(type)
35             if (isValidate) {
36                 const img = document.createElement('img');
37                 img.src = window.URL.createObjectURL(file); //***生成文件路径，添加到img的src
38                 const sizeChanged = getSize(size);
39                 const textContent = document.createTextNode(name + ': ' + sizeChanged);
40                 li.appendChild(textContent);
41                 li.appendChild(img);                
42             } else {
43                 const textContent = document.createTextNode("InValide File Type");
44                 li.appendChild(textContent);
45             }
46             return li;
47         }
48         function getSize(size) { // 按照用户习惯计算大小
49             if (size<1024) {
50                 return size + 'byte';
51             } else if (size<1048576) {
52                 return (size/1024).toFixed(1) + 'KB';
53             } else {
54                 return (size/1048576).toFixed(1) + 'MB';
55             }
56         }
57         const fileTypes = ['image/png', 'image/jpeg'];
58         function validateFileType(type) { // 验证文件类型
59             if (!fileTypes.includes(type)) {
60                 return false;
61             }
62             return true;
63         }
64     </script>
65 </body>
66 </html>