如何在 JS 中通过键对值进行分组和连接

Question

我尝试像疯子一样对对象数组进行某种合并/按键排序。 不知道为什么，但我不知道该怎么做。

我的应用在 Ionic / Angular 中。

这是我所拥有的：

[
  {
      "2021": {
          "a": "aText"
      }
  },
  {
      "2021": {
          "b": "bText"
      }
  },
  {
      "2020": {
          "z": "zText"
      }
  },
  {
      "2020": {
          "y": "yText"
      }
  },
  {
      "2020": {
          "x": "xText"
      }
  }
]

我的目标是得到这个：

[
  {
      "2021": { "a": "aText", "b": "bText" }
  },
  {
      "2020": { "z": "zText", "y": "yText", "x": "xText" }
  }
]

换句话说，我想按年份重新组合并连接它们。

有人知道怎么做吗？

Answer 1

如果您只想要一个以年份作为键的对象，那么它只是一个标准的“分组依据”，带有一个嵌套循环来迭代每个对象的 Object.entries()。如果您确实想要最初发布的输出（单个对象的数组），您可以 map() 返回的分组对象的全部内容并使用 Object.fromEntries() 将每个对象转换为一个对象

const input = [
  { 2021: { a: 'aText' } },
  { 2021: { b: 'bText' } },
  { 2020: { z: 'zText' } },
  { 2020: { y: 'yText' } },
  { 2020: { x: 'xText' } },
];

const grouped_object = input.reduce(
  (a, o) => (Object.entries(o).forEach(([y, o]) => (a[y] = { ...(a[y] ?? {}), ...o })), a),
  {}
);

// if you just want a single object with years as keys
console.log(grouped_object);

const grouped_array = Object.entries(grouped_object)
  .map(([year, data]) => ({[year]: data}));

// the output from your question
console.log(grouped_array);

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

或重构为使用for...of 循环和Object.assign()

const input = [
  { 2021: { a: 'aText' } },
  { 2021: { b: 'bText' } },
  { 2020: { z: 'zText' } },
  { 2020: { y: 'yText' } },
  { 2020: { x: 'xText' } },
];

const grouped_object = {};
for (const obj of input) {
  for (const [year, data] of Object.entries(obj)) {
    grouped_object[year] = Object.assign(grouped_object[year] ?? {}, data);
  }
}

// if you just want a single object with years as keys
console.log(grouped_object);

// or avoiding computed properties
const grouped_array = Object.entries(grouped_object)
  .map(([year, data]) => (o={}, o[year]=data, o));

// the output from your question
console.log(grouped_array);

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

Answer 2

最好使用对象按年份分组。这是一个使用reduce 遍历数组以生成该对象的示例。

const data=[{2021:{a:"aText"}},{2021:{b:"bText"}},{2020:{z:"zText"}},{2020:{y:"yText"}},{2020:{x:"xText"}}];

const out = data.reduce((acc, obj) => {

  // Get the key and value from the object that in
  // the current iteration
  const [ [ key, value ] ] = Object.entries(obj);

  // If the key doesn't exist on the accumulator (the initial
  // object that we passed into the `reduce`) create an empty object
  acc[key] = acc[key] || {};

  // Update the value of that object property with
  // the value of the object
  acc[key] = { ...acc[key], ...value };

  // Return the updated object for the next iteration
  return acc;

// Here's the initial object that
// acts as the accumulator through all the iterations
}, {});

console.log(out);

或者使用数组来保存每年的信息：

const data=[{2021:{a:"aText"}},{2021:{b:"bText"}},{2020:{z:"zText"}},{2020:{y:"yText"}},{2020:{x:"xText"}}];

const out = data.reduce((acc, obj) => {

  const [ [ key, value ] ] = Object.entries(obj);

  // Use an array instead of an object
  acc[key] = acc[key] || [];

  // Push the first element of the Object.values
  // into the array
  acc[key] = [ ...acc[key], Object.values(value)[0] ];

  return acc;

}, {});

console.log(out);

其他文档

• Object.entries

• Object.values

• Destructuring assignment

• Spread syntax