圖片上傳時即時顯示2

<script language="javascript" type="text/javascript"> 
var allowExt = ['jpg', 'gif', 'bmp', 'png', 'jpeg']; 
var preivew = function(file, container){  
	try{  
		var pic = new Picture(file, container);  
	}catch(e){  
		alert(e);  
	} 
}    
var Picture = function(file, container){  
var height = 0,   widht = 0,   ext = '',  size = 0,  name  = '',  path  = '';  
var self = this;  
if(file){     
	name = file.value;  
	if (window.navigator.userAgent.indexOf("MSIE")>=1){    
		file.select();    
		path = document.selection.createRange().text;   
	}else if(window.navigator.userAgent.indexOf("Firefox")>=1){    
		if(file.files){    
			path = file.files.item(0).getAsDataURL();    
		}else{   
			path = file.value;   
		}  
	}   
}else{  
	throw "bad file";  
}   
ext = name.substr(name.lastIndexOf("."), name.length);  
if(container.tagName.toLowerCase() != 'img'){  
	throw "container is not a valid img label";  
	container.visibility = 'hidden';  
}  
container.src = path;  
container.alt = name;  
container.style.visibility = 'visible';  
height = container.height;  
widht = container.widht;  
size  = container.fileSize;  
this.get = function(name){  
					return self[name];  
					}  
		this.isValid = function(){  
		if(allowExt.indexOf(self.ext) !== -1){   
			throw 'the ext is not allowed to upload';   
			return false;  
		}  
	} 
}
</script>
<div class='previewDemo'>
  <input id="file" type="file" onchange="preivew(this, document.getElementById('img'));">
  <img id="img" style="visibility:hidden" height="100px" width="100px"></div>