如何总结对象数组中相同字段的值？

Question

我有一个对象数组

const data = [
  { category: 'shopping', amount: 50 }, 
  { category: 'rent', amount: 1000 }, 
  { category: 'groceries', amount: 20 }, 
  { category: 'shopping', amount: 50 }
]

我正在尝试总结每个类别的金额

const result = [
  { category: 'shopping', amount: 100 },
  { category: 'rent', amount: 1000 },
  { category: 'groceries', amount: 20 }
]

到目前为止，我正在考虑删除类别的“重复项”并将它们存储到一个数组中

const temp = data.map((obj) => {
  return obj.category
})

const categories = [...new Set(temp)] // ['shopping','rent','groceries']

有了以上内容，我正在考虑做一个嵌套循环，但经过多次尝试，我失败了。

任何帮助表示赞赏

Answer 1

您可以使用reduce()来做到这一点。

迭代给定数据，如果存在与当前项目具有相同category的项目，则添加amount ，否则将当前项目添加为新条目。

 const data = [ { category: 'shopping', amount: 50 }, { category: 'rent', amount: 1000 }, { category: 'groceries', amount: 20 }, { category: 'shopping', amount: 50 } ]; let result = data.reduce((acc, curr) => { let item = acc.find(item => item.category === curr.category); if (item) { item.amount += curr.amount; } else { acc.push(curr); } return acc; }, []); console.log(result);

这是使用 object 作为累加器的替代方法。 这具有性能优势，因为我们不必在每次迭代时调用find() 。 感谢frodo2975的建议。

 const data = [ { category: 'shopping', amount: 50 }, { category: 'rent', amount: 1000 }, { category: 'groceries', amount: 20 }, { category: 'shopping', amount: 50 } ]; let result = Object.values(data.reduce((acc, curr) => { let item = acc[curr.category]; if (item) { item.amount += curr.amount; } else { acc[curr.category] = curr; } return acc; }, {})); console.log(result);

Answer 2

我将专注于有效计算每个类别的总数，然后以您需要的格式重组数据。 所以是这样的：

// Construct an object mapping category to total amount.
const totals = data.reduce((totals, { category, amount }) => {
    totals[category] = (totals[category] || 0) + amount;
}, {});

// Format the data as you like.
const result = Object.entries(totals).map(([category, amount]) => ({ category, amount });

Answer 3

只是使用reduce方法的另一个版本:)

 const data = [ { category: 'shopping', amount: 50 }, { category: 'rent', amount: 1000 }, { category: 'groceries', amount: 20 }, { category: 'shopping', amount: 50 } ]; const result = data.reduce((a,c) => { a[c.category] = a[c.category] || {category: c.category, amount: 0}; a[c.category].amount += c.amount; return a; }, {}) console.log(Object.values(result));