我有这个对象数组

[{
    tag: 'james'
  },
  {
    tag: 'james'
  },
  {
    tag: 'john'
  }
]

如何计算并生成如下所示的新数组?
[{
  tag: 'james',
  count: 2
}, {
  tag: 'john',
  count: 1
}]

我尝试使用 reduce 生成的对象而不是对象数组。

const arr = [{tag: 'james'},{tag: 'james'},{tag: 'john'}];
let newArr = arr.reduce((accum, arr) => {
  accum[arr.tag] = ++accum[arr.tag] || 1
  return accum
}, {})

console.log(newArr)

最佳答案

创建一个对象而不是数字,最后使用 Object.values 方法从对象中获取这些值。

// just extract values from the object as an array
let res = Object.values(arr.reduce((accum, o) => {
  // initialize object if not defined already
  accum[o.tag] = accum[o.tag] || { ...o, count: 0  }
  // increment count property
  accum[o.tag].count++;
  return accum
}, {}))

let arr = [{tag: 'james'},{tag: 'james'},{tag: 'john'}]

let res = Object.values(arr.reduce((accum, o) => {
  accum[o.tag] = accum[o.tag] || { ...o, count: 0 }
  accum[o.tag].count++;
  return accum
}, {}))

console.log(res)



您甚至可以通过使用用于对象/索引引用的附加变量来直接创建数组。
// an object for keeping reference
let ref = {};

let res = arr.reduce((accum, o) => {
  // check reference already defined, if not define refernece and push to the array
  ref[o.tag] || accum.push(ref[o.tag] = { ...o, count: 0 })
  // update count using the refernece keeped in the object
  ref[o.tag].count++;
  return accum
}, []);

let arr = [{tag: 'james'},{tag: 'james'},{tag: 'john'}]

let ref = {};

let res = arr.reduce((accum, o) => {
  ref[o.tag] || accum.push(ref[o.tag] = { ...o, count: 0 })
  ref[o.tag].count++;
  return accum
}, []);

console.log(res)

关于javascript - 计算对象属性的重复数组以生成新数组,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/55469468/

10-14 18:08
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