javascript - 如何组合具有相同键的对象而不覆盖值？

Question

我试图通过相同的键组合对象数组，而不是覆盖这些值。是否可以将这些值组合到一个数组中以引用相同的键引用。

考虑这个日历对象:

const calendar = [
   {date: "1999", month: "03"},
   {date: "1999", month: "01"},
   {date: "1998", month: "04"}
]

// My attempted with lodash:
let results = _(calendar )
    .groupBy('date')
    .value()

// my output (also returns an object)
results = {
     1998: {date: "1998", month: "04"}
     1999: {date: "1999", month: "03"}, {date: "1999", month: "01"}
}

// Acceptable Output #1: 
results = [
   {date: "1999", month: ["03", "01"]},
   {date: "1998", month: ["04"]}
]

// Acceptable Output #2:
results = {
     1998: [{month: "04"}]
     1999: [{month: "03"}, {month: "01"}]
}

// Acceptable Output #3:
results = [
   {"1999": ["03", "01"]},
   {"1998": ["04"]}
]

或者如果有其他可行的替代方案。最终目标是不覆盖我在 stackoverflow 上看到的所有值......

Answer 1

您可以使用 reduce 而不是使用 lodash 库。

输出 3

const calendar = [
  {date: "1999", month: "03"},
  {date: "1999", month: "01"},
  {date: "1998", month: "04"}
];

const output = calendar
.reduce((a, {date, month}) => {
  if(!a[date]) {
    a[date] = [];
  }
  
  a[date].push(month);
  return a;
}, {});

console.log(output);

输出 2

const calendar = [
  {date: "1999", month: "03"},
  {date: "1999", month: "01"},
  {date: "1998", month: "04"}
];

const output = calendar
.reduce((a, {date, month}) => {
  if(!a[date]) {
    a[date] = [];
  }
  
  a[date].push({month});
  return a;
}, {});

console.log(output);

输出 1

const calendar = [
  {date: "1999", month: "03"},
  {date: "1999", month: "01"},
  {date: "1998", month: "04"}
];

const output = calendar
.reduce((a, {date, month}) => {
  if(!a[date]) {
    a[date] = {date, month: []};
  }

  a[date].month.push(month);
  return a;
}, {});

console.log(Object.values(output));