上传图片及时预览

1     <img id="imgTag" style="height: 100px;" />
2     <input type="file" onchange="DisplayImage(this,‘imgTag‘)"/>

function DisplayImage(fileTag,imgTagId){
    var allowExtention=".jpg.png.gif";
    var extentionArr=fileTag.value.split(‘.‘);
    var extention = extentionArr[extentionArr.length-1];
    if(!(allowExtention.indexOf(extention)>-1)){
        alert("Please upload image!");
    }else{
        //for adveced broswer(the newest ie,chrome,ff)
        if(typeof(FileReader)!=="undefined"){
            var reader = new FileReader();
            reader.readAsDataURL(fileTag.files[0]);
            reader.onload = function(e){
                document.getElementById(imgTagId).setAttribute("src", e.target.result);
            }
        }else{
        //for(ie6)
        document.getElementById(imgTagId).setAttribute("src",fileTag.value);
        }
    }
}