js排序--一道js数据结构题

给一个数组：

[{ GroupMark: "", GroupName: "hao", SendTime: '123', SendContent: "1ha" },
{ GroupMark: "1", GroupName: "hao", SendTime: '123', SendContent: "2ha" },
{ GroupMark: "1", GroupName: "hao", SendTime: '123', SendContent: "3ha" },
{ GroupMark: "22", GroupName: "hao", SendTime: '123', SendContent: "4ha" },
{ GroupMark: "3", GroupName: "hao", SendTime: '123', SendContent: "6ha" },
{ GroupMark: "22", GroupName: "hao", SendTime: '123', SendContent: "5ha" }]

目标

[{"GroupMark":"","GroupName":"hao","SendTime":"123","SendContent":["1ha"]},
{"GroupMark":"1","GroupName":"hao","SendTime":"123","SendContent":["2ha","3ha"]},
{"GroupMark":"22","GroupName":"hao","SendTime":"123","SendContent":["4ha","5ha"]},
{"GroupMark":"3","GroupName":"hao","SendTime":"123","SendContent":["6ha"]}]

//参照数组去重的
var arr =[{ GroupMark: "", GroupName: "hao", SendTime: '123', SendContent: "1ha" },
{ GroupMark: "1", GroupName: "hao", SendTime: '123', SendContent: "2ha" },
{ GroupMark: "1", GroupName: "hao", SendTime: '123', SendContent: "3ha" },
{ GroupMark: "22", GroupName: "hao", SendTime: '123', SendContent: "4ha" },
{ GroupMark: "3", GroupName: "hao", SendTime: '123', SendContent: "6ha" },
{ GroupMark: "22", GroupName: "hao", SendTime: '123', SendContent: "5ha" }]
var tempObj ={}
var resArr = []
for(let [index,item] of arr.entries() ){
    let {GroupMark,GroupName,SendContent} = item
    let keyStr = GroupMark+'&'+GroupName
    if(tempObj[keyStr]){
        let tempSendContent= tempObj[keyStr].SendContent
        tempObj[keyStr].SendContent=[...tempSendContent,SendContent]
    }else{
        tempObj[keyStr]={
            ...item,
            SendContent:[SendContent]
        }
    }
}
for (let item in tempObj) {
    resArr.push(tempObj[item])
}
console.log(resArr)