文件上传常见问题整理

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文件上传：<input type="file" /> （IE9及以下不支持下面这些功能，其它浏览器最新版本均已支持。）

1、允许上传文件数量

允许选择多个文件：<input type="file" multiple>
只允许上传一个文件：<input  type="file" single>

2、上传指定的文件格式

<input type="file" accept="image/gif,image/png" />

这里的上传格式仅指打开上传弹窗选择文件时默认的文件格式，可手动修改成其它文件格式。

如果不限制上传图片的格式可写成：accept="image/*"

其它格式参考如下：

*.3gpp   audio/3gpp, video/3gpp    3GPP Audio/Video
*.ac3    audio/ac3    AC3 Audio
*.asf    allpication/vnd.ms-asf    Advanced Streaming Format
*.au     audio/basic    AU Audio
*.css    text/css    Cascading Style Sheets
*.csv    text/csv    Comma Separated Values
*.doc    application/msword    MS Word Document
*.dot    application/msword    MS Word Template
*.dtd    application/xml-dtd    Document Type Definition
*.dwg    image/vnd.dwg    AutoCAD Drawing Database
*.dxf    image/vnd.dxf    AutoCAD Drawing Interchange Format
*.gif    image/gif    Graphic Interchange Format
*.htm    text/html    HyperText Markup Language
*.html   text/html    HyperText Markup Language
*.jp2    image/jp2    JPEG-2000
*.jpe    image/jpeg    JPEG
*.jpeg   image/jpeg    JPEG
*.jpg    image/jpeg    JPEG
*.js     text/javascript, application/javascript    JavaScript
*.json   application/json    JavaScript Object Notation
*.mp2    audio/mpeg, video/mpeg    MPEG Audio/Video Stream, Layer II
*.mp3    audio/mpeg    MPEG Audio Stream, Layer III
*.mp4    audio/mp4, video/mp4    MPEG-4 Audio/Video
*.mpeg   video/mpeg    MPEG Video Stream, Layer II
*.mpg    video/mpeg    MPEG Video Stream, Layer II
*.mpp    application/vnd.ms-project    MS Project Project
*.ogg    application/ogg, audio/ogg    Ogg Vorbis
*.pdf    application/pdf    Portable Document Format
*.png    image/png    Portable Network Graphics
*.pot    application/vnd.ms-powerpoint    MS PowerPoint Template
*.pps    application/vnd.ms-powerpoint    MS PowerPoint Slideshow
*.ppt    application/vnd.ms-powerpoint    MS PowerPoint Presentation
*.rtf    application/rtf, text/rtf    Rich Text Format
*.svf    image/vnd.svf    Simple Vector Format
*.tif    image/tiff    Tagged Image Format File
*.tiff   image/tiff    Tagged Image Format File
*.txt    text/plain    Plain Text
*.wdb    application/vnd.ms-works    MS Works Database
*.wps    application/vnd.ms-works    Works Text Document
*.xhtml  application/xhtml+xml    Extensible HyperText Markup Language
*.xlc    application/vnd.ms-excel    MS Excel Chart
*.xlm    application/vnd.ms-excel    MS Excel Macro
*.xls    application/vnd.ms-excel    MS Excel Spreadsheet
*.xlt    application/vnd.ms-excel    MS Excel Template
*.xlw    application/vnd.ms-excel    MS Excel Workspace
*.xml    text/xml, application/xml    Extensible Markup Language
*.zip    aplication/zip    Compressed Archive

 3、FileList上传文件数组

FileList对象都是一组文件对象的集合，而文件对象则拥有下列的属性：
name – 文件名（不包含路径）
type – 文件的MIME类型（小写）
size – 文件的尺寸（单位为字节）

lastModifiedDate 为上传文件的最后修改时间

通过上面的几个对象，我们能够控制用户上传的文件大小和文件类型，以便减轻服务器再次检测时的压力，并提升安全系数

var a=document.getElementById("file");
a.onchange=function(e){
	e=e || window.event;
	var b=e.target.files;
	alert(b[0].name);
}

4、拖动上传
dataTransfer 对象
dropEffect[=sCursorStyle]
设置或获取拖拽操作的类型和要显示的光标类型
copy：复制样式被显示
link：链接样式被显示
move：移动样式被显示
none：默认,没有鼠标样式被定义

effectAllowed[=sEffect]
设置或获取数据传送操作可应用与该对象的源元素
copy 选项被复制
link  选项被dataTransfer作为link方式保存
move  当放置时,对象被移动至目标对象
copylink  选项是被复制还是被作为link方式保存关键在于目标对象
linkmove 选项是被作为link方式保存还是被移动关键在于目标对象
all 所有效果都被支持
none 不支持任何效果
uninitialized 默认不能通过这个属性传递任何值

setData(sFormat,sData)     将指定格式的数据赋值给dataTransfer或者clipboardData     sFormat:URL,Text
getData(sFormat)     从dataTransfer或者clipboardData中获取值     sFormat:URL,Text
clearData([sFormat])     通过dataTransfer或者clipboardData中删除某种格式的数据     sFormat:Text,URL,File,HTML,Image

<!DOCTYPE HTML> 
<html> 
<head> 
<meta charset="utf-8"> 
<title></title> 
<style type="text/css">
#DropZone{border:1px solid #CCC;height:50px;}
</style>
</head>
<body>
<input type="file" multiple accept="image/gif,image/png" id="file">
<div id="DropZone"></div>
<div id="Lists"></div>
<script>
var aa=document.getElementById("file");
aa.onchange=function(){
	fileDrop();
}
 
function fileDrop(e) {
    e = e || window.event;
     
    e.stopPropagation(); // 阻止冒泡
    e.preventDefault();  //阻止默认行为
     
    var files = e.dataTransfer.files;   //FileList
     
    var output = [];
     
    for(var i = 0, f; f = files[i]; i++) {
        output.push(‘<li><strong>‘ + f.name + ‘</strong>(‘ + f.type + ‘) - ‘ + f.size +‘ bytes</li>‘);
    }
     
    document.getElementById(‘Lists‘).innerHTML = ‘<ul>‘ + output.join(‘‘) + ‘</ul>‘;
};
 
function dragOver(e) {
    e = e || window.event;
     
    e.stopPropagation();
    e.preventDefault();
    e.dataTransfer.dropEffect = ‘copy‘; //指定拖放视觉效果
};
var d = document.getElementById(‘DropZone‘);
 
try {
    d.addEventListener(‘dragover‘, dragOver, false);
    d.addEventListener(‘drop‘, fileDrop, false)
} catch(ex) {
    document.write(‘something must be wrong!‘);
}
 
</script>
</body>
</html>

5、FileReader文件预览，读取文件数据（同时可读取图片文件宽高）
FileReader包含四种异步读取文件的方式：
FileReader.readAsBinaryString(Blob|File) - result属性包含的是file/blob的二进制字符串形式的数据。每个字节由一个0-255的整数表示。
FileReader.readAsText(Blob|File, opt_encoding) - result属性包含的是以文本方式表示的file/blob数据。默认情况下，字符串以‘UTF-8‘编码方式解码。使用opt_encoding参数可以指定一个不同的格式。
FileReader.readAsDataURL(Blob|File) - result属性包含的是以data URL编码的file/blob数据。
FileReader.readAsArrayBuffer(Blob|File) - result属性包含的是以ArrayBuffer对象表示的file/blob数据。
一旦这些read方法被调用，onloadstart, onprogress, onload, onabort, onerror, onloadend就可以被用来追踪进度。

<!DOCTYPE HTML> 
<html> 
<head> 
<meta charset="utf-8"> 
<title></title> 
<style type="text/css">
body{margin:0;padding:0;}
img{vertical-align:bottom;}
</style>
</head>
<body>
<input type="file" multiple accept="image/gif,image/png,,image/jpeg" id="Files">
<div id="Preview"></div>
<ul id="Errors"></ul>
<script>
function fileSelect(e) {
    e = e || window.event;
     
    var files = e.target.files;  //FileList Objects    
    var ireg = /image/.*/i,
        p = document.getElementById(‘Preview‘);
         
    var ul = document.getElementById(‘Errors‘);
    for(var i = 0, f; f = files[i]; i++) {
        if(!f.type.match(ireg)) {
            //设置错误信息
            var li = document.createElement(‘li‘);
            li.innerHTML = ‘<li>‘ + f.name +‘不是图片文件.</li>‘;
             
            ul.appendChild(li);
             
            continue;
        }
         
        var reader = new FileReader();
         
        reader.onload = (function(file) {
            return function(e) {
                var span = document.createElement(‘span‘);
				var img = new Image;
				img.alt=file.name;
				img.onload = function() {
					console.log(img.height); // image is loaded; sizes are available
				};
 
				img.src=this.result;
                span.innerHTML = ‘<img class="thumb" src="‘+ this.result +‘" alt="‘+ file.name +‘" />‘;
                 
                p.insertBefore(span, null);
            };
        })(f);
        //读取文件内容
        reader.readAsDataURL(f);
    }
}
     
if(window.File && window.FileList && window.FileReader && window.Blob) {
    document.getElementById(‘Files‘).addEventListener(‘change‘, fileSelect, false);
} else {
    document.write(‘您的浏览器不支持File Api‘);
}
</script>
</body>
</html>

上传txt文件内容预览(需对<>&‘"|等符号进行过滤否则会中断读取)：

<!DOCTYPE HTML> 
<html> 
<head> 
<meta charset="utf-8"> 
<title></title> 
<style type="text/css">
body{margin:0;padding:0;}
img{vertical-align:bottom;}
</style>
</head>
<body>
<input type="file" multiple id="Files">
<div id="Preview"></div>
<ul id="Errors"></ul>
<script>
function encodeHTML(source) {  
	//return source;
    return source  
            .replace(/&/g, ‘&‘)  
            .replace(/</g, ‘<‘)  
            .replace(/>/g, ‘>‘)
            .replace(/"/g, ‘"‘);
};  
function fileSelect(e) {  
    e = e || window.event;  
       
    var files = e.target.files;  //FileList Objects      
    var ireg = /text/.*/i,  
        p = document.getElementById(‘Preview‘);  
           
    var ul = document.getElementById(‘Errors‘);  
    for(var i = 0, f; f = files[i]; i++) {  
        console.log(f.type);  
        if(!f.type.match(ireg)) {  
            //设置错误信息  
            var li = document.createElement(‘li‘);  
            li.innerHTML = ‘<li>‘ + f.name +‘不是文本文件.</li>‘;  
               
            ul.appendChild(li);  
               
            continue;  
        }  
           
        var reader = new FileReader();  
           
        reader.onload = (function(file) {  
            return function(e) {  
                var div = document.createElement(‘div‘);  
                div.className = "text"  
                div.innerHTML = encodeHTML(this.result);  
                   
                p.insertBefore(div, null);  
            };  
        })(f);  
        //读取文件内容  
        reader.readAsText(f);  
    }  
}  
       
if(window.File && window.FileList && window.FileReader && window.Blob) {  
    document.getElementById(‘Files‘).addEventListener(‘change‘, fileSelect, false);  
} else {  
    document.write(‘您的浏览器不支持File Api‘);  
}  
</script>
</body>
</html>

读取上传txt指定区域文本内容：

<!DOCTYPE HTML> 
<html> 
<head> 
<meta charset="utf-8"> 
<title></title> 
<style type="text/css">
body{margin:0;padding:0;}
img{vertical-align:bottom;}
</style>
</head>
<body>
<input type="file" multiple id="Files">
<button type="button" id="buttons" data-start="0" data-end="3">确定</button>
<div id="range"></div>
<div id="content"></div>
<script>
 
function readBlob(start, end) {  
    var files = document.getElementById(‘Files‘).files;  
       
    if(!files.length) {  
        alert(‘请选择文件‘);  
        return false;  
    }  
       
    var file = files[0],  
        start = parseInt(start, 10) || 0,  
        end = parseInt(end, 10) || (file.size - 1);  
           
    var r = document.getElementById(‘range‘),  
        c = document.getElementById(‘content‘);  
           
    var reader = new FileReader();  
 
    reader.onloadend = function(e) {  
        if(this.readyState == FileReader.DONE) {  
            c.textContent = this.result;  
            r.textContent = "Read bytes: " + (start + 1) + " - " + (end + 1) + " of " + file.size + " bytes";  
        }  
    };  
 
    var blob;  
        
    blob = file.slice(start, end + 1, ‘text/plain;charset=UTF-8‘);  
    reader.readAsBinaryString(blob);  
};  
   
try {  
    document.getElementById(‘buttons‘).addEventListener(‘click‘, function(e) {  
        if(e.target.tagName.toLowerCase() == ‘button‘) {  
            var start = e.target.getAttribute(‘data-start‘),  
                end = e.target.getAttribute(‘data-end‘);  
                   
            readBlob(start, end);  
        }    
    });  
} catch(ex) {  
    alert(‘something error happens!‘)  
}  
</script>
</body>
</html>

File接口提供了slice方法支持把文件切成不同的片段,第一个参数是起始的字节数,第二个参数是结束的字节数，还有一个可选的内容类型字符串可以作为第三个参数。早期的chrome和firefox版本不支持file.slice   可使用file.webkitSlice和file.mozSlice替代，最新版本均支持file.slice。

6、文件读取进度 
<!DOCTYPE HTML> 
<html> 
<head> 
<meta charset="utf-8"> 
<title></title> 
</head>
<body>
<form>  
    <fieldset>  
        <legend>分度读取文件：</legend>  
        <input type="file" id="File" />  
        <input type="button" value="中断" id="Abort" />  
        <p>  
            <label>读取进度：</label><progress id="Progress" value="0" max="100"></progress>  
        </p>  
        <p id="Status"></p>  
    </fieldset>  
</form>  
 
<script>
var h = {  
    init: function() {  
        var me = this;  
           
        document.getElementById(‘File‘).onchange = me.fileHandler;  
        document.getElementById(‘Abort‘).onclick = me.abortHandler;  
           
        me.status = document.getElementById(‘Status‘);  
        me.progress = document.getElementById(‘Progress‘);  
        me.percent = document.getElementById(‘Percent‘);  
           
        me.loaded = 0;  
        //每次读取1M  
        me.step = 1024 * 1024;  
        me.times = 0;  
    },  
    fileHandler: function(e) {  
        var me = h;  
           
        var file = me.file = this.files[0];  
        var reader = me.reader = new FileReader();  
           
        //  
        me.total = file.size;  
           
        reader.onloadstart = me.onLoadStart;  
        reader.onprogress = me.onProgress;  
        reader.onabort = me.onAbort;  
        reader.onerror = me.onerror;  
        reader.onload = me.onLoad;  
        reader.onloadend = me.onLoadEnd;  
        //读取第一块  
        me.readBlob(file, 0);
    },  
    onLoadStart: function() {  
        var me = h;  
    },  
    onProgress: function(e) {  
        var me = h;  
           
        me.loaded += e.loaded;  
        //更新进度条  
        me.progress.value = (me.loaded / me.total) * 100;  
    },  
    onAbort: function() {  
        var me = h;  
    },  
    onError: function() {  
        var me = h;  
           
    },  
    onLoad: function() {  
        var me = h;  
   
        if(me.loaded < me.total) {  
            me.readBlob(me.loaded);  
        } else {  
            me.loaded = me.total;  
        }  
    },  
    onLoadEnd: function() {  
        var me = h;  
           
    },  
    readBlob: function(start) {  
        var me = h;  
           
        var blob,  
            file = me.file;  
           
        me.times += 1;  
           
        if(file.slice) {  
            blob = file.slice(start, start + me.step + 1);  
        } else if(file.mozSlice) {  
            blob = file.mozSlice(start, start + me.step + 1);  
        }  
           
        me.reader.readAsText(blob);  
    },  
    abortHandler: function() {  
        var me = h;  
           
        if(me.reader) {  
            me.reader.abort();  
        }  
    }  
};  
   
h.init();  
</script>
</body>
</html>

本文代码以chrome测试为主。

 

参考资料：

http://blog.csdn.net/zhu1988renhui/article/details/7936498

http://blog.csdn.net/zhu1988renhui/article/details/7936525

http://dev.w3.org/2006/webapi/FileAPI/#dfn-filereader

http://www.html5rocks.com/zh/tutorials/file/dndfiles/

http://www.w3.org/TR/file-upload/

http://www.w3.org/TR/file-upload/#dfn-filereader

http://www.w3.org/TR/file-upload/#dfn-Blob

http://www.w3.org/TR/file-upload/#dfn-fileerror

http://www.w3.org/TR/progress-events/#Progress

http://www.zhangxinxu.com/wordpress/?p=1923

http://www.tfan.org/wp-content/slides/file.html#1

 

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