javascript - 如何在javascript中获取json数组中的重复对象

Question

我有一个像这样的 JSON 数组:

var data = [
      {title: "HH02"},
      {title: "HH03"},
      {title: "HH04"},
      {title: "HH02"},
      {title: "HH07"},
      {title: "HH08"},
      {title: "HH08"},
      {title: "HH10"},
      {title: "HH02"},
      {title: "HH11"}
]

首先，我想在 JSON 数组中获取重复的对象，如下所示:

var output = [
     {title: "HH02" },
     {title: "HH08" },
]

然后我想获取所有重复的对象以及它们在另一个 JSON 数组中重复的次数，如下所示

var output = [
     {title: "HH02" , repeat: 3},
     {title: "HH08" , repeat: 2},
]

我尝试这样做，但效果不佳:

data.map(v => v.title).sort().sort((a, b) => {
                    if (a === b) output.push(a);
                })

Answer 1

您可以使用减少、过滤和映射

• 首先按标题对所有值进行分组，计算重复次数
• 过滤出现一次或少于一次的标题(排除它们)
• 映射它们以获得所需的输出

var data = [{title: "HH02"},{title: "HH03"},{title: "HH04"},{title: "HH02"},{title: "HH07"},{title: "HH08"},{title: "HH08"},{title: "HH10"},{title: "HH02"},{title: "HH11"}]

let final = [...data.reduce((op, inp) => {
  let title = inp.title
  op.set(title, (op.get(title) || 0) + 1)
  return op
}, new Map()).entries()].filter(([_,repeat]) => repeat > 1).map(([title, repeat]) => ({
  title,
  repeat
}))

console.log(final)