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HomeWeb Front-endH5 Tutorial用HTML5轻松实现图片预览

        在网页中实现图片上传功能,当用户选择了图片文件后,想在页面中即时预览该图片,这个简单的需求在很久很久以前可以实现,后来因为安全性的问题被禁止直接访问本地文件了,所以又在很长很长一段时间里,想通过HTML直接预览用户选择的图片变得不可能,自从有了HTML5,这个功能又回来了,通过FileReader可以轻松的实现这个功能。

  只要在3e701519c4bde102649c97eab49f5c17文件表单元素中监听 onchange 事件,然后通过FileReader读取图片文件,然后将读取的内容在用HTML5轻松实现图片预览中显示即可。示例代码如下:

document.getElementById('file').onchange = function(evt) {
    
// 如果浏览器不支持FileReader,则不处理
    
if
 (window.FileReader) 
return
;
    var files = evt.target.files;
    
for
 (var i = 0, f; f = files[i]; i++) {
        
if
 (!f.type.match('image.*')) {
            
continue
;
        }
        var reader = 
new
 FileReader();
        reader.onload = (function(theFile) {
            
return
 function(e) {
                
// img 元素
                document.getElementById('previewImage').src = e.target.result;
            };
        })(f);
        reader.readAsDataURL(f);
    }
}

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