linq to js 用法

        /**
      * 排序汇总
      * */
     var result = Enumerable.From(vm.productList).GroupBy("$.goods_id", null,
         function (key, g) {
             var result = {
                 currency: key,
                 total: g.Sum(c => parseInt(c.num == " " ? 0 : c.num))
             }
             return result;
         }).ToArray();
 
 /**
* FirstOrDefault 获取第一个
* */
     vm.productList.forEach(function (item) {
         var arrRes = Enumerable.From(result).FirstOrDefault(-1,x => x.currency == item.goods_id);
         if (arrRes != "" && arrRes != null && arrRes != undefined && arrRes.currency == item.goods_id) {
             
             item.FOrderByNum = parseInt(arrRes.total) ;
         }
     })
        //排序
     var productList = Enumerable.From(vm.productList).OrderByDescending("x=>x.FOrderByNum").ToArray();//降序OrderByDescending()