js检查上传图片大小和类型

<meta http-equiv="Content-Type" content="text/html; charset=gb2312">

照片：
<div id='phototd'>
    <input type="file" name="photo" class="input"  id="photo"  onChange="UserUtil.initTestImg(this);setTimeout('UserUtil.checkPhoto()',100)" />
</div>
<hr>

<script language="javascript">

    var $=function(id){return document.getElementById(id);}

    var UserUtil={
        photo_suffix : 'jpg|gif',
        photo_size : 100,
        photo_html : null,
        test_img : new Image(),
        img_size : 0,
        init : function(){
            this.photo_html=$('phototd').innerHTML;
            this.test_img.onload=function(){
                UserUtil.img_size=UserUtil.test_img.fileSize;
            };
        },
        initTestImg : function(obj){
            this.test_img.src=obj.value;
        },
        checkPassword : function(){
            var password =  $('password').value;
            var repassword =  $('rePassword').value;
            var msg = repassword == password ? '' : '<font color="red">密码不一致,请确认!</font>';    
            $('passwordErrorMsg').innerHTML = msg;
            return msg=='';
        },
        checkPhoto : function(){
            var photo=$('photo');
            if(!this.checkSuffix(photo.value)){
                alert("对不起，您选择的图片类型不对，请选择以下图片类型："+this.photo_suffix);
                this.resetFile();
                return false;
            }
            if(navigator.userAgent.indexOf('Firefox')>0)
                this.img_size=photo.files.item(0).fileSize;
            if(this.img_size/1024>this.photo_size){
                alert("上传图片容量太大，选择的图片容量不能超过：" + (this.photo_size)+"K");
                this.resetFile();
                return false;
            }
            return true;
        },
        checkSuffix : function(path){
            if(path.lastIndexOf('.')<0)
                return false;
            var fileName=path.substring(path.lastIndexOf('.')+1);
            var suffixs=this.photo_suffix.split('|');
            for(var i=0 ; i<suffixs.length ; i++){
                if(fileName.toLowerCase()==suffixs[i].toLowerCase())
                    return true;
            }
            return false;
        },
        resetFile : function(){
            $('phototd').innerHTML=this.photo_html;
        },
        save : function(){
            if(Validator.Validate($('userForm'),3) && this.checkPassword() && checkPhoto())
                $('userForm').submit();
        }
    };
    UserUtil.init();
</script>