lodash group by and sum

var data=[{value:1200,count:5},{value:1200,count:10},{value:1230,count:5},{value:1240,count:5}];
console.log(_.chain(data)
    .groupBy("value")
    .map(function(value, key) {
        return [key, _.reduce(value, function(result, currentObject) {
            return {
                value: currentObject.value,
                count: result.count+ currentObject.count
            }
        }, {
            value: 0,
            count: 0
        })];
    })
    .object()
    .value());

　　lodash js数组分组汇总