[英]use flatmap on javascript, with condition
我正在创建一个处理监视和编辑权限的组件。 我用来保存权限的数据结构如下所示:
const input = [{
isAllowed: true,
permissionType: "watch",
userId: 14
},
{
isAllowed: false,
permissionType: "edit",
userId: 14
},
{
isAllowed: true,
permissionType: "edit",
userId: 24
},
{
isAllowed: false,
permissionType: "edit",
userId: 34
},
{
isAllowed: false,
permissionType: "watch",
userId: 44
},
{
isAllowed: false,
permissionType: "edit",
userId: 44
}
]
起初,我只是想获取所有具有任何权限的用户的列表,所以我会使用
let managers = _.flatMap(props.settings.managerPermissions, (p) => p.userId);
managers = [...new Set(managers)];
所以这会给我留下managers = [14,24,34,44]
,但我需要编辑这个平面图,这样我就不会找回根本没有权限的经理的 ID,即使他们是已经添加到列表中,所以在这种情况下,新平面图的返回值应该是managers = [14,24]
。 (当然 flatMap 在这里不是必须的,如果有更好的方法,我会很高兴看到它)
当 map 的结果是 arrays 的数组时,您只需要 flatMap,并且您需要一个平面数组。
在这种情况下,通过isAllowed
过滤数组,然后将 map 过滤到userId
:
const arr = [{"isAllowed":true,"permissionType":"watch","userId":14},{"isAllowed":false,"permissionType":"edit","userId":14},{"isAllowed":true,"permissionType":"edit","userId":24},{"isAllowed":false,"permissionType":"edit","userId":34},{"isAllowed":false,"permissionType":"watch","userId":44},{"isAllowed":false,"permissionType":"edit","userId":44}] const managers = [...new Set( arr.filter(o => o.isAllowed).map(o => o.userId) )] console.log(managers)
但是,您实际上对 map 使用Array.flatMap()
(或 lodash 等效项)并同时进行过滤。 地图/过滤器组合不太惯用,我不确定性能,所以我自己不使用它。 这个想法是为您不想要的项目返回一个空数组:
const arr = [{"isAllowed":true,"permissionType":"watch","userId":14},{"isAllowed":false,"permissionType":"edit","userId":14},{"isAllowed":true,"permissionType":"edit","userId":24},{"isAllowed":false,"permissionType":"edit","userId":34},{"isAllowed":false,"permissionType":"watch","userId":44},{"isAllowed":false,"permissionType":"edit","userId":44}] const managers = [...new Set( arr.flatMap(o => o.isAllowed? o.userId: []) )] console.log(managers)
您应该能够过滤掉isAllowed=false
然后做同样的事情 - 尽管flatMap
似乎没用(因为没有数组嵌套) - 只需使用map
const input = [ {isAllowed: true, permissionType: "watch", userId: 14 }, {isAllowed: false, permissionType: "edit", userId: 14 }, {isAllowed: true, permissionType: "edit", userId: 24 }, {isAllowed: false, permissionType: "edit", userId: 34 }, {isAllowed: false, permissionType: "watch", userId: 44 }, {isAllowed: false, permissionType: "edit", userId: 44 }] const managers = [...new Set(input.filter(x => x.isAllowed).map(x => x.userId))]; console.log(managers);
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