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,TextgetData(sFormat) 从dataTransfer或者clipboardData中获取值 sFormat:URL,TextclearData([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。
到此这篇关于JavaScript文件上传问题整理的文章就介绍到这了。希望对大家的学习有所帮助，也希望大家多多支持Devmax。