javascript - 查找相同键值的 JSON 对象的长度

Question

我有一个 JSON 文件。我想找到一个键值对相似的 JSON 对象的长度。就像，

https://api.myjson.com/bins/h5mgv

[
  {
    "receive_date": "2013-11-04",
    "responses": "2",
    "name": "west"
  },
  {
    "receive_date": "2013-11-04",
    "responses": "8668",
    "name": "west"
  },
  {
    "receive_date": "2013-11-13",
    "responses": "121",
    "name": "east"
  }
]

在上面的示例中，长度为 2，其中 "name": "west"长度为 1，其中 "name": "east" 。我想迭代 JSON 并找到键 name 的相同值使用 JavaScript。输出应该看起来像，

east : 1
west : 2

通过使用 length()我可以找到整个 JSON 的长度，但是推荐的方法来查找相同键值的长度。

Answer 1

您可以使用reduce来获取一个新对象，列出每个名称的计数:

const myArray = [
  {
    "receive_date": "2013-11-04",
    "responses": "2",
    "name": "west"
  },
  {
    "receive_date": "2013-11-04",
    "responses": "8668",
    "name": "west"
  },
  {
    "receive_date": "2013-11-13",
    "responses": "121",
    "name": "east"
  }
]

const myCounts = myArray.reduce((counts, item) => {
  if (counts[item.name] === undefined) counts[item.name] = 0;
  counts[item.name]++;
  return counts;
}, {});

console.log(myCounts);

这会产生结果:

{
  "west": 2,
  "east": 1
}