图片上传预显示图片最简单办法

<input class="uploadImg" type="file" name="uploadfile2" id="file3">
<div class="fileimg3"></div>

<script type="text/javascript">
 $('#file3').change(function(){
            function getObjectURL(file) {
                var url = null;
                if (window.createObjcectURL != undefined) {
                    url = window.createOjcectURL(file);
                } else if (window.URL != undefined) {
                    url = window.URL.createObjectURL(file);
                } else if (window.webkitURL != undefined) {
                    url = window.webkitURL.createObjectURL(file);
                }
                return url;
            }
            var objURL = getObjectURL(this.files[0]);//这里的objURL就是input file的真实路径
            $('.fileimg3').html("<img src='" + objURL + "' alt='Alternate Text' width='640px' height='350px' id='target' />");
        });
</script>