javascript - GroupBy并以无点样式减少对象数组

我最近开始使用Ramda并试图找到一种无点方法来编写一种减少对象数组的方法。

这是对象数组:

const someObj = [
    {
        name: 'A',
        city: 1,
        other: {
            playtime: 30
        }
    },
    {
        name: 'B',
        city: 2,
        other: {
            playtime: 20
        }
    },
    {
        name: 'c',
        city: 1,
        other: {
            playtime: 20
        }
    }
];

我正在尝试使用像poinfree这样的ramda减少对象

{
    '1': {
        count: 2,
        avg_play_time: 20 + 30 / count
    },
    '2': {
        count: 1,
        avg_play_time: 20 / count
    }
}

我可以使用减少数组的方法来做到这一点，但不确定如何用ramda pointfree样式编写相同的内容。任何建议将不胜感激。

最佳答案

一种解决方案是做这样的事情:

// An optic to extract the nested playtime value
// Coupled with a `lift` operation which allows it to be applied over a collection
// Effectively A -> B => A[] -> B[]
const playtimes = R.lift(R.path(['other', 'playtime']))

R.pipe(
  // Group the provided array by the city value
  R.groupBy(R.prop('city')),
  // Return a body specification which computes each property based on the
  // provided function value.
  R.map(R.applySpec({
    count: R.length,
    average: R.pipe(playtimes, R.mean)
  }))
)(someObj)