Question

我有一个JSON文件，其中有超过2万个条目，并且在Spotify上具有不同轨道的名称。我试图计算特定歌手播放每首歌曲的次数。

   NavigationView {
    VStack {
        ...
    }.frame(maxHeight:.infinity,  alignment: .top)
      .padding()
.border(Color.red).navigationBarTitle("", displayMode: .inline)
   }

这是我目前的代码。基本上，它的工作是循环遍历function countInArray(array, what) { var count = 0; for (var i = 0; i < array.length; i++) { if (array[i] === what) { count++; } } nfPlays.push(count) return count; } nfSongs2 = [] nfSongs = [] nfPlays = [] for(var i = 0; i < dta.length; i++) { if(dta[i].artistName === "NF") { nfSongs.push(dta[i].trackName) } } for(var i = 0; i < dta.length; i++) { if(nfSongs2.indexOf(dta[i].trackName) === -1 && dta[i].artistName === "NF") { nfSongs2.push(dta[i].trackName) } } for(var i = 0; i < nfSongs2.length; i++) { console.log(`${nfSongs2[i]} has ${countInArray(nfSongs, nfSongs2[i])} plays`) } console.log(countInArray(nfSongs, "WHY")) console.log(nfPlays) console.log(nfSongs2) console.log(nfSongs)数组，并按NF（特别是轨道名称）获取所有包含重复项的条目，然后再次执行此操作，但是这次仅捕获唯一的名称。然后，我在曲目的所有唯一名称上运行dta，它将获取播放次数并将其推送到countInArray数组中。

不是特别复杂，它确实可以工作。我想知道是否有更好，更短的方法。

Answer 1

我认为您应该尝试filter方法。例如：

function countInArray(array, what) {
    const foundItems = array.filter(value => value === what);
    nfPlays.push(foundItems.length)
    return foundItems.length;
}

或

const foundTracks = dta.filter(track => track.artistName === "NF");

Background

Answer 2

您可以使用比数组（indexOf）呈现更快查询的Map

const dta = [
  { trackName:'a', artistName:'NF' },
  { trackName:'a', artistName:'NF' },
  { trackName:'b', artistName:'NF' },
  { trackName:'b', artistName:'other' },
]
const trackNameToCount = dta.reduce((m, track) => {
  if (track.artistName === 'NF') {
    const n = m.get(track.trackName) || 0
    m.set(track.trackName, n+1)
  }
  return m
}, new Map())

;[...trackNameToCount.entries()].forEach(([name, count]) => {
  console.log(`${name} played ${count} times`)
})

Answer 3

希望我了解您在做什么。我建议使用对象类型来处理重复项。像这样吗？

dta = [
  {trackName: "dog", artistName: "NF"},
  {trackName: "dog", artistName: "mack"},
  {trackName: "dog", artistName: "NF"},
  {trackName: "cat", artistName: "fred"},
  {trackName: "mouse", artistName: "NF"},
]

nfsongs = {}

dta.forEach(item => {
    if (item.artistName==="NF") {
        if (item.trackName in nfsongs) {
            nfsongs[item.trackName]++;
        } else {
            nfsongs[item.trackName]=1;
        }
    }
})

for (key in nfsongs) {
    console.log(`${key} has ${nfsongs[key]} plays`)
}

是否有更好的方法遍历大型数组以查找每个项目的编号？

3 个答案: