function ChangeDateFormat(cellval) {
    try {
        var date = new Date(parseInt(cellval.replace("/Date(", "").replace(")/", ""), 10));
        var month = date.getMonth() + 1 < 10 ? "0" + (date.getMonth() + 1) : date.getMonth() + 1;
        var currentDate = date.getDate() < 10 ? "0" + date.getDate() : date.getDate();
        return date.getFullYear() + "-" + month + "-" + currentDate;
    } catch (e) {
        return "";
    }
}

------解决方案--------------------
专程实体类或者实体类集合吗？给你个类
   /// <summary>
   /// Json工具类
   /// </summary>
   public static class JSONUtils
   {
       /// <summary>
       /// 序列化数据为Json数据格式.
       /// </summary>
       /// <param name="value">被序列化的对象</param>
       /// <returns></returns>
       public static string ToJson(this object value)
       {

           Type type = value.GetType();

           Newtonsoft.Json.JsonSerializer json = new Newtonsoft.Json.JsonSerializer();
           json.NullValueHandling = NullValueHandling.Ignore;
           json.ObjectCreationHandling = Newtonsoft.Json.ObjectCreationHandling.Replace;
           json.MissingMemberHandling = Newtonsoft.Json.MissingMemberHandling.Ignore;
           json.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
           StringWriter sw = new StringWriter();
           Newtonsoft.Json.JsonTextWriter writer = new JsonTextWriter(sw);
           writer.Formatting = Formatting.None;
           writer.QuoteChar = '"';
           json.Serialize(writer, value);

           string output = sw.ToString();
           writer.Close();
           sw.Close();

           return output;
       }
       /// <summary>
       /// 将Json数据转为对象
       /// </summary>
       /// <typeparam name="T">目标对象</typeparam>
       /// <param name="jsonText">json数据字符串</param>
       /// <returns></returns>
       public static T FromJson<T>(this string jsonText)
       {
           Newtonsoft.Json.JsonSerializer json = new Newtonsoft.Json.JsonSerializer();

           json.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;
           json.ObjectCreationHandling = Newtonsoft.Json.ObjectCreationHandling.Replace;
           json.MissingMemberHandling = Newtonsoft.Json.MissingMemberHandling.Ignore;
           json.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;

           StringReader sr = new StringReader(jsonText);
           Newtonsoft.Json.JsonTextReader reader = new JsonTextReader(sr);
           T result = (T)json.Deserialize(reader, typeof(T));
           reader.Close();

           return result;
       }
   }






//转换成json     JSONUtils.ToJson(类);
//转换成实体类    JSONUtils.FromJson<类的名字>(json字符串)