<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<title>Document</title>
</head>
<body>
<input type="file" id="btnFile" />
</body>
</html>
<script>
var btn = document.getElementById('btnFile');
btn.onchange = function(){
getSize(this);
function getSize(t){
var size;
if(t.files){
size = parseInt( t.files[0].size / 1024 /1024,10);
}else{
size = parseInt( new ActiveXObject("Scripting.FileSystemObject").GetFile(t.value).size / 1024/1024,10 );
}
if( size >= 2){
alert('文件过大');
}
};
</script>