Question

当前，我正在尝试计算对象数组中的多次出现并将最终计数推入其中。我不想将数据存储在其他数组中。数据应保留在现有数据中。

我要添加计数的数组：

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

我当前的示例代码从数组中删除/减少了代码，因此最终结果不是所希望的：

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

array = Object.values(array.reduce((r, { artist, venue }) => {
    r[artist] = r[artist] || { artist, venue, count: 0 };
    r[artist].count++;
    return r;
}, {}));

console.log(array);

Which logs:
    { artist: 'metallica', venue: 'olympiastadion', count: 3 },
    { artist: 'foofighters', venue: 'wuhlheide', count: 2 },
    { artist: 'deftones', venue: 'columbiahalle', count: 1 },
    { artist: 'deichkind', venue: 'wuhlheide', count: 1 }

我正在尝试达到以下结果：

var array = [
    { artist: 'metallica', venue: 'olympiastadion', count: 3 },
    { artist: 'foofighters', venue: 'wuhlheide', count: 2 },
    { artist: 'metallica', venue: 'columbiahalle', count: 3 },
    { artist: 'deftones', venue: 'columbiahalle', count: 1 },
    { artist: 'deichkind', venue: 'wuhlheide', count: 1 },
    { artist: 'metallica', venue: 'wuhlheide', count: 3 },
    { artist: 'foofighters', venue: 'trabrennbahn', count: 2 }
];

很高兴能帮助我指出正确的方向。

感谢您的帮助！所需的解决方案是：

var array = [{ artist: 'metallica', venue: 'olympiastadion' }, { artist: 'foofighters', venue: 'wuhlheide' }, { artist: 'metallica', venue: 'columbiahalle' }, { artist: 'deftones', venue: 'columbiahalle' }, { artist: 'deichkind', venue: 'wuhlheide' }, { artist: 'metallica', venue: 'wuhlheide' }, { artist: 'foofighters', venue: 'trabrennbahn' }],
    map = array.reduce( 
        (map, { artist }) => map.set(artist, (map.get(artist) || 0) + 1),
        new Map
    ),
    array = array.map(o => Object.assign({}, o, { count: map.get(o.artist) }));

console.log(array);

Answer 1

您可以先遍历所有项目，然后将旧对象和新的count属性分配给新对象，从而获得计数。

var array = [{ artist: 'metallica', venue: 'olympiastadion' }, { artist: 'foofighters', venue: 'wuhlheide' }, { artist: 'metallica', venue: 'columbiahalle' }, { artist: 'deftones', venue: 'columbiahalle' }, { artist: 'deichkind', venue: 'wuhlheide' }, { artist: 'metallica', venue: 'wuhlheide' }, { artist: 'foofighters', venue: 'trabrennbahn' }],
    map = array.reduce( 
        (map, { artist }) => map.set(artist, (map.get(artist) || 0) + 1),
        new Map
    ),
    result = array.map(o => Object.assign({}, o, { count: map.get(o.artist) }));

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

您可以按照以下步骤进行操作：

使用reduce()从数组创建对象，该对象具有所有唯一艺术家的数量
该对象将具有与artists不同的键，其值将作为其计数。
然后在原始数组上使用forEach。
将所有count设置为计数数组中当前项目的演出者的值。

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

const unique = array.reduce((ac,{artist:a}) => (ac[a] = ac[a] + 1 || 1,ac),{});
array.forEach(x => x.count = unique[x.artist]);
console.log(array)

Answer 3

您可以对数组进行一次遍历，以建立艺术家姓名映射到计数，然后进行第二遍修改每个数组项以添加与艺术家相关的计数。

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

var counts = array.reduce((counts, item) => {
  var artistName = item.artist;
  if (counts[artistName]) {
    counts[artistName] += 1;
  } else {
    counts[artistName] = 1;
  }
  
  return counts;
}, {});

array.forEach(item => item.count = counts[item.artist])

console.log(array);

为清楚起见，.reduce函数很冗长，但可以大大缩短：

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

var counts = array.reduce((counts, item) => (counts[item.artist] = counts[item.artist] || 1, counts), {});

console.log(counts);

如果要创建一个 new 数组而不是修改旧数组中的对象，则可以复制每个对象和该数组：

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

var counts = {
  "metallica": 3,
  "foofighters": 2,
  "deftones": 1,
  "deichkind": 1
}

var newArray = array.map(item => ({...item, count: counts[item.artist]}))

console.log(newArray);
console.log(array);

Answer 4

您可以在数组上迭代两次。

var array = [
    { artist: 'metallica', venue: 'olympiastadion' },
    { artist: 'foofighters', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'columbiahalle' },
    { artist: 'deftones', venue: 'columbiahalle' },
    { artist: 'deichkind', venue: 'wuhlheide' },
    { artist: 'metallica', venue: 'wuhlheide' },
    { artist: 'foofighters', venue: 'trabrennbahn' }
];

array.forEach(a => {
  if (!a.hasOwnProperty('count')) {
    Object.assign(a, { count: 0 });
  }
  array.forEach(b => {
    if (a.artist === b.artist) {
      a.count++;
    }
  });
});

console.log(array);

如何在对象数组中查找多次出现并添加计数值？

4 个答案: