javascript - 有没有办法对这个对象数组进行分组或减少

Question

下面的示例，获取与 period_str 的相同值相对应的总数学值关键。

[
     {math: 40, period_str: "Period 1, 03 2019"},
     {math: 32, period_str: "Period 1, 03 2019"},
     {math: 44, period_str: "Period 1, 02 2020"},
]

预期输出

[
{math: 72, period_str: "Period 1, 03 2020"}
{math: 44, period_str: "Period 1, 02 2020"}
]

或者 输出(仅对象)

{math: 72, period_str: "Period 1, 03 2020"}
{math: 44, period_str: "Period 1, 02 2020"}

Answer 1

您可以仅使用period_str作为唯一键:

const arr = [
 {math: 40, period_str: "Period 1, 03 2019"},
 {math: 32, period_str: "Period 1, 03 2019"},
 {math: 44, period_str: "Period 1, 02 2020"},
]

const out = arr.reduce((a, v) => {
  if(a[v.period_str]) {
    a[v.period_str].math += v.math
  } else {
    a[v.period_str] = v
  }
  return a
}, {})

console.log(Object.values(out))