Javascript 计算分配给对象属性的唯一值总数

Question

我的数据库查询返回一个对象数组，如下所示:

[
    {"id":18,"newStory":"Stormy"},
    {"id":19,"newStory":"Russia"},
    {"id":20,"newStory":"Stormy"},
    {"id":21,"newStory":"Witch Hunt"},
    {"id":22,"newStory":"Stormy"},
    {"id":23,"newStory":"Russia"}
]

我需要每个独特的 newStory 的故事总数。然后，我想遍历这些总数，生成类似于以下数组的内容:

newStoryTotal["Stormy"][2]
newStoryTotal["Witch Hunt"][1]
newStoryTotal["Russia"][3]

我曾尝试使用 reduce 和 lodash，但我缺乏这方面的专业知识。我也知道这可以使用嵌套的数据库查询来完成，但我试图通过单个查询 + Javascript 进行计数来完成。

Answer 1

你可以使用一个简单的reduce:

const data = [
  { id: 18, newStory: 'Stormy' },
  { id: 19, newStory: 'Russia' },
  { id: 20, newStory: 'Stormy' },
  { id: 21, newStory: 'Witch Hunt' },
  { id: 22, newStory: 'Stormy' },
  { id: 23, newStory: 'Russia' }
]

const output = data.reduce((a, {newStory:s}) => (a[s] = (a[s] || 0) + 1, a), {})
console.log(output)

当然，如果您很难阅读一行，您可以随时将其写出来以提高可读性:

const data = [
  { id: 18, newStory: 'Stormy' },
  { id: 19, newStory: 'Russia' },
  { id: 20, newStory: 'Stormy' },
  { id: 21, newStory: 'Witch Hunt' },
  { id: 22, newStory: 'Stormy' },
  { id: 23, newStory: 'Russia' }
]

const output = data.reduce((accumulator, object) => {
  if (accumulator[object.newStory] !== undefined) {
    accumulator[object.newStory]++
  } else {
    accumulator[object.newStory] = 1
  }
  return accumulator
}, {})
console.log(output)