[转]html5表单上传控件Files API

表单上传控件：<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

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){

<span style="white-space:pre">    </span>e=e || window.event;

<span style="white-space:pre">    </span>var b=e.target.files;

<span style="white-space:pre">    </span>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。

上传图片预览：

<!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>

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

本文代码以chrome测试为主。