js從陣列中獲取月份和年份

我有一個物件陣列：

let arr = [
    {date: '2021/01/23', a1: 'text1', a2: 'text2' },
    {date: '2021/11/21', a1: 'text1', a2: 'text2' },
    {date: '2020/12/22', a1: 'text1', a2: 'text2' },
    {date: '2021/12/08', a1: 'text1', a2: 'text2' },
    {date: '2020/12/14', a1: 'text1', a2: 'text2' },
    {date: '2021/10/25', a1: 'text1', a2: 'text2' },
    {date: '2021/12/04', a1: 'text1', a2: 'text2' },
  ]

如何使用年份過濾每個月的物件陣列，例如：

'December 21' = [
{date: '2021/12/04', a1: 'text1', a2: 'text2' },
{date: '2021/12/08', a1: 'text1', a2: 'text2' }
]

'January 21' = [
{date: '2021/01/23', a1: 'text1', a2: 'text2' }
]

'December 20' = [
{date: '2020/12/22', a1: 'text1', a2: 'text2' }
]

提前致謝！：）

uj5u.com熱心網友回復：

你可以嘗試這樣的事情：

// Your input
let arr = [
    {date: '2021/01/23', a1: 'text1', a2: 'text2' },
    {date: '2021/11/21', a1: 'text1', a2: 'text2' },
    {date: '2020/12/22', a1: 'text1', a2: 'text2' },
    {date: '2021/12/08', a1: 'text1', a2: 'text2' },
    {date: '2020/12/14', a1: 'text1', a2: 'text2' },
    {date: '2021/10/25', a1: 'text1', a2: 'text2' },
    {date: '2021/12/04', a1: 'text1', a2: 'text2' },
];

// Month dictionary
const monthNames = [ "January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December" ];

// Get what you want
const result = arr.reduce((acc, el) => {
  // Extract year & month from date
  const [ year, month ] = el.date.split('/');
  // Get label in 'Month YY' format
  const label = monthNames[ month - 1]   ' '   year.slice(2);
  // Add object key to result if necessary
  if (!acc[label]) acc[label] = [];
  // Save element
  acc[label].push(el);
  return acc;
}, {});

console.log(result);

參考：Array.prototype.reduce()

uj5u.com熱心網友回復：

我會做這樣的事情：

const filterArr = (month, year) => arr.filter(x => {
  const splitDate = x.date.split('/');
  return splitDate[0] === year && splitDate[1] === month;
});

// Usage
filterArr("10", "2021");

編輯：如果你想使用月份的名稱試試這個：

const monthNames = ["January", "February", "March", "April", "May", "June", "July",
  "August", "September", "October", "November", "December"];

const monthNameToNumber = (month) => (monthNames.indexOf(month)   1)
      .toString().padStart(2, '0');

// Usage
monthNameToNumber("December"); // "12"

uj5u.com熱心網友回復：

您可以使用 forEach 方法從陣列中進行迭代并將所有內容保存在一個物件中。像這樣：

let arr = [
  {date: '2021/01/23', a1: 'text1', a2: 'text2' },
  {date: '2021/11/21', a1: 'text1', a2: 'text2' },
  {date: '2020/12/22', a1: 'text1', a2: 'text2' },
  {date: '2021/12/08', a1: 'text1', a2: 'text2' },
  {date: '2020/12/14', a1: 'text1', a2: 'text2' },
  {date: '2021/10/25', a1: 'text1', a2: 'text2' },
  {date: '2021/12/04', a1: 'text1', a2: 'text2' },
];

filteredArr = {};

arr.forEach((obj) => {
  const newDate = new Date(obj.date);
  const stringMonthAndYear = newDate.toLocaleString('default', { month: 'long' })   ' '   newDate.getFullYear();

  if (filteredArr[stringMonthAndYear] && filteredArr[stringMonthAndYear].length) {
    filteredArr[stringMonthAndYear].push(obj);
  } else {
    filteredArr[stringMonthAndYear] = [obj];
  }
});

console.log(filteredArr);

uj5u.com熱心網友回復：

試試這個

const month = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

let arr = [
  { date: '2021/01/23', a1: 'text1', a2: 'text2' },
  { date: '2021/11/21', a1: 'text1', a2: 'text2' },
  { date: '2020/12/22', a1: 'text1', a2: 'text2' },
  { date: '2021/12/08', a1: 'text1', a2: 'text2' },
  { date: '2020/12/14', a1: 'text1', a2: 'text2' },
  { date: '2021/10/25', a1: 'text1', a2: 'text2' },
  { date: '2021/12/04', a1: 'text1', a2: 'text2' },
];

let obj = {};
for (const row of arr) {
  const date = new Date(Date.parse(row.date));
  let key = `${month[date.getMonth()]} ${date.getFullYear()}`;
  if(!obj[key]) obj[key] = [];
  obj[key].push(row);
}

標籤：javascript 数组 目的

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