js单个图片上传预览

<input type="file" onchange="showImg(this,'img')" accept="image/*" />
<img id="img" style="width:100%;height: 100%;padding:1px;" src="null"/>
<script type="text/javascript">
    //上传图片后立即预览 file对象,图片容器id
    function showImg(fileObj, imgId) {
     
     
        var file = fileObj.files[0];
        var r = new FileReader();
        r.readAsDataURL(file);
        $(r).load(function () {
     
     
            $('#' + imgId).attr("src", this.result);
        })
    }

</script>