js 数组封装方法实现类似sql的groupBy分组求和。

      function GroupBy(datas,keys,callBack) {
          const list = datas || [];
          const groups = [];
          list.forEach(v => {
              const key = {};
              const data = {};
              keys.forEach(k => {
                  key[k] = v[k];
              });
              let group = groups.find(v => {
                  return v._key === JSON.stringify(key);
              });
              if (!group) {
                  group = {
                      _key:JSON.stringify(key),
                      key: key,
                  };
                  groups.push(group);
              }
              if(callBack){
                  group.data = callBack(group.data,v);
                  group.total=group.total||0;
                  group.total++;
              }else {
                  group.data=group.data||[];
                  group.data.push(v);
              }
          });
          return groups;
      }

        window.onload=function () {
            const data = [
                {key:1,key2:1,v:123},
                {key:1,key2:1,v:55},
                {key:2,key2:1,v:85},
                {key:1,key2:2,v:15},
                {key:2,key2:1,v:99}
            ];
            var d = GroupBy(data,['key','key2'],(d,v)=> {
                d = d||0;
                return d+=v.v;
            });
            console.log(d);
            var a = GroupBy(data,['key','key2']);
            console.log(a);
        };