mongodb mapreduce返回错误的答案

Question

我将以下数据存储在集合“订单”中 data in collection

我必须找到状态为F的每个客户的最大数量

我尝试了以下操作，但答案错误

> var mapfunction =function(){if(this.status=='F') emit(this.cus_id,this.amount);}
> var reducefunction=function(key,value){return Math.max(...value);}
> db.Order.mapReduce(mapfunction,reducefunction,{out:'total7'})
{
    "result" : "total7",
    "timeMillis" : 528,
    "counts" : {
        "input" : 6,
        "emit" : 2,
        "reduce" : 0,
        "output" : 2
    },
    "ok" : 1
}
>  db.total7.find()
{ "_id" : "A1", "value" : 200 }
{ "_id" : "C1", "value" : 200 }