Question

我正在使用以下Lodash链接的实用程序来映射/平面和数组并生成一个新的，同时排除未定义的值。

SELECT  AVG(outertable.dis) AS disaverage, outertable.yr,
        outertable.pitcher AS pitcher,
        outertable.pitch_type AS pitch_type, outertable.war, outertable.gs,
        outertable.temp, rsgames2.ATTEND_PARK_CT, rsgames2.DAYNIGHT_PARK_CD,
        rsgames2.WIND_SPEED_PARK_CT, teamdata.LNPop, teamdata.PPMult,
        teamdata.FCI
    FROM  
      ( SELECT  distinct sqrt(((abs((power(pitches.px- myavgtable.apx, 2)) +
                     power(pitches.pz-myavgtable.apz,2))))) AS dis, myavgtable.yr,
                myavgtable.pitcher, myavgtable.pitch_type, myavgtable.war,
                myavgtable.gs, myavgtable.temp, myavgtable.game_id, myavgtable.HOME
            FROM  
              ( SELECT  distinct atbats.pitcher AS pitcher, YEAR(games2.DATE) AS yr,
                        pitches.pitch_type AS pitch_type, pitches.pitch_type AS pt,
                        AVG(pitches.px) AS apx,
                        AVG(pitches.pz) AS apz,
                        pitcherwar.WAR as war,
                        pitcherwar.GS as gs,
                        games2.temp as temp,
                        games2.game_id AS game_id, games2.HOME as HOME
                    from  atbats
                    join pitches on pitches.ab_id = atbats.ab_id
                    join pitcherwar on atbats.pitcher = pitcherwar.eliasid
                    join games2 on atbats.game_id = games2.game_id
                    where  atbats.pitcher = games2.home_starting_pitcher
                      AND  atbats.pitcher = pitcherwar.eliasid
                      AND  pitches.pitch_type != 'IN'
                      AND  pitches.pitch_type != 'PO'
                      AND  pitches.pitch_type != 'UN'
                      AND  YEAR(games2.DATE)>=2008
                    group by  atbats.pitcher, pitches.pitch_type, yr
              ) AS myavgtable
            JOIN atbats  ON atbats.pitcher=myavgtable.pitcher
            JOIN pitches  ON atbats.ab_id=pitches.ab_id
            JOIN games2 on atbats.game_id=games2.game_id 
      ) AS outertable
    JOIN rsgames2 on outertable.game_id = rsgames2.game_id
    JOIN teamdata on outertable.HOME = teamdata.Team
      and  outertable.yr = teamdata.Year
    WHERE  outertable.dis IS NOT NULL
    GROUP BY  outertable.pitcher, outertable.pitch_type, outertable.yr;

这就是结果：

如您所见，仍然包含未定义的值。这是为什么？

修改

resp.data看起来像这样

const array = _(resp.data)
   .omit(_.isUndefined)
   .flatMap('building')
   .value()
console.log(array)

EDIT2：

这些[ { username: '', building: [ name: '' ] } { username: '', building: [ name: '' ] } // etc... ]值可能是对象所拥有的空undefined。

Answer 1

额外undefined值应属于user中resp.data，其中不存在building。您要做的就是_.filter() undefined之后_.identity()到_.flatMap()的所有值_.omit。

注意：使用_.flatMap()只能用于对象，在数组的上下文中使用它（例如_.filter()导致数组）将产生一个对象的结果，其中索引为每个项目都是数组中的索引。您应该使用var data = [ { username: 'user1', building: [ { name: 'building1' } ] }, { username: 'user2', building: [ { name: 'building2' } ] }, { username: 'user3' } ]; var result = _(data) .flatMap('building') .filter(_.identity) .value(); document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');代替。

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.11.2/lodash.js"></script>

＆＃13;

{{1}}

＆＃13;

Answer 2

试试这个。

const array = _(resp.data)
.omit(_.isUndefined)
.flatMap('building')
.map()
.omit(_.isUndefined)
.value()

为什么omit（）在映射后没有删除未定义的值？

2 个答案: