数组对象如何根据对象中某个字段分组

function  groupByType(arr,param) {
            var map = {},
                dest = [];
            for(var i = 0; i < arr.length; i++){
                var ai = arr[i];
                if(ai[param] && !map[ai[param]]){
                    dest.push({
                        name: ai[param],
                        data: [ai]
                    });
                    map[ai[param]] = ai;
                }else{
                    for(var j = 0; j < dest.length; j++){
                        var dj = dest[j];
                        if(dj.name == ai[param]){
                            dj.data.push(ai);
                            break;
                        }
                    }
                }
            }
            return dest;
        }