layui上傳圖片

HTML代碼： 

<div class="layui-col-sm4">
      <label class="layui-form-label">上傳圖片：</label>
      <div class="layui-upload">
           <button type="button" class="layui-btn" id="test1">上傳圖片</button>
           <div class="layui-upload-list">
                <img class="layui-upload-img" id="demo1" name="thumb">
                <p id="demoText"></p>
            </div>
       </div>
</div>

JS代碼：

layui.use(['form','layer','laydate','upload'], function(){
        $ = layui.jquery;
        var form = layui.form,
            upload = layui.upload,
            laydate = layui.laydate
            ,layer = layui.layer;

        //執行一個upload實例   logo圖片上傳
        var uploadInst =upload.render({
            elem: '#test1'
            ,url: '後端鏈接'
            ,accept: 'file' //普通文件
            ,size:1024
            ,before: function(obj){
                //預讀本地文件示例，不支持ie8
                obj.preview(function(index, file, result){
                    $('#demo1').css('display', "block"); //圖片鏈接（base64）
                    $('#demo1').attr('src', result); //圖片鏈接（base64）
                });
            }
            ,done: function(res){
                //如果上傳失敗
                if(res.status >1){
                    return layer.msg('上傳失敗');
                }
                //上傳成功
                $("#file").val(res.data)
            }
            ,error: function(){
                //演示失敗狀態，並實現重傳
                var demoText = $('#demoText');
                demoText.html('<span style="color: #FF5722;">上傳失敗</span> <a class="layui-btn layui-btn-xs demo-reload">重試</a>');
                demoText.find('.demo-reload').on('click', function(){
                    uploadInst.upload();
                });
            }
        });
})