<!doctype html public "-//w3c//dtd html 4.01//en" "http://www.w3.org/tr/html4/strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>JS上传图片前的图片预览效果</title>
</head>
<body>
<input id="myfile" type="file" />
<br />
<img src="/images/logo.gif" alt="Image to be upload." />
<div id="info"></div>
<script type="text/javascript">
var dFile = document.getElementById('myfile');
var dImg = document.getElementsByTagName('img')[0];
var dInfo = document.getElementById('info');
dFile.onchange = function(){
if(!dFile.value.match(/.jpg|.gif|.png|.bmp/i)){alert('File type must be: .jpg, .gif, .bmp or .png !');return;}
if(dFile.files){
dImg.src = dFile.files[0].getAsDataURL();
}else if(dFile.value.indexOf('\\') > -1 || dFile.value.indexOf('\/') > -1){
dImg.src = dFile.value;
}
}
</script>
</body>
</html>