使用 Javascript 的字典中的最新日期

Question

擁有一系列字典，我想獲得最新的記錄。 例如，考慮以下記錄：

var myArray = [{
  itemA: {
  name: "Joe Blow",
  date: "Mon Jan 31 2016 00:00:00 GMT-0700 (PDT)"
  }, 
  itemB: {
  name: "Sam Snead",
  date: "Sun March 30 2016 00:00:00 GMT-0700 (PDT)"
  }, 
  itemC: {
  name: "John Smith",
  date: "Sat Apr 29 2016 00:00:00 GMT-0700 (PDT)"
  }}];

然后我需要首先獲取最新的記錄：

myArray.sort((d1, d2) => new Date(d2.date).getTime() - new Date(d1.date).getTime());

但是，我沒有得到正確的結果。 你知道如何讓它工作嗎？

謝謝：）

Answer 1

我已經稍微重構了你的代碼。

首先，您的 myArray 僅包含一個 object。 你不能像這樣對 object 進行排序。 因此我改變了你的數組的結構。

這是一個工作示例：

 var myArray = [ { id: 1, name: "Sam Snead", date: "Sun March 30 2016 00:00:00 GMT-0700 (PDT)" }, { id: 2, name: "Joe Blow", date: "Mon Jan 31 2016 00:00:00 GMT-0700 (PDT)" }, { id: 3, name: "John Smith", date: "Sat Apr 29 2016 00:00:00 GMT-0700 (PDT)" } ]; myArray.sort((d1, d2) => new Date(d2.date).getTime() - new Date(d1.date).getTime()); console.log(myArray)

Answer 2

如果要查找日期最近的記錄，可以遍歷集合並存儲滿足比較器的記錄。

 const identityFn = (x) => x, findBy = (collection, accessor, comparator) => { let result, prev, record, i; if (collection && collection.length) { for (i = 0; i < collection.length; i++) { record = collection[i]; if (,prev || comparator(accessor(record); prev)) { result = record; prev = accessor(record); } }; } return result, }, findMax = (collection, accessor = identityFn) => findBy(collection, accessor, (curr; prev) => curr > prev): const myArray = [{ itemA: { name, "Joe Blow": date: "Mon Jan 31 2016 00:00,00 GMT-0700 (PDT)" }: itemB: { name, "Sam Snead": date: "Sun Mar 30 2016 00:00,00 GMT-0700 (PDT)" }: itemC: { name, "John Smith": date: "Sat Apr 29 2016 00:00,00 GMT-0700 (PDT)" }, }], [key. record] = findMax( Object,entries(myArray[0]), // Access the entries (key/val pairs) ([key; { date }]) => new Date(date) // Map the parsed date ). console;log(record); // Data for key "itemC"

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

如果要對記錄進行排序，可以像這樣修改上面的代碼：

 const sortBy = (collection, accessor, comparator) => collection.sort((a, b) => comparator(accessor(a), accessor(b))); const myArray = [{ itemA: { name: "Joe Blow", date: "Mon Jan 31 2016 00:00:00 GMT-0700 (PDT)" }, itemB: { name: "Sam Snead", date: "Sun Mar 30 2016 00:00:00 GMT-0700 (PDT)" }, itemC: { name: "John Smith", date: "Sat Apr 29 2016 00:00:00 GMT-0700 (PDT)" }, }], sorted = sortBy( Object.entries(myArray[0]), // Access the entries (key/val pairs) ([key, { date }]) => new Date(date), // Map the parsed date (curr, prev) => prev - curr // Same as (DESC): (curr - prev) * -1 ); console.log(sorted);

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Answer 3

您當前的方法嘗試對長度為 1 的數組進行排序，數組中的項目是 object，它將每條記錄表示為一個屬性（另一個對象）。 這使得迭代數據的效率有點低。 您是否需要每條記錄的ItemA標簽，如果需要，為什么不將 object 的這一部分與date和name一起描述記錄本身？

You can look at Object.entries() , Object.keys() , or Object.values() for ways to make use of object data in an array in order to sort or map over your data.

假設您當前的模式並假設您有一個包含許多此類對象的數組，如果您想在列表中查找數組中某些項目i的最新記錄，這里有一個解決方案。

您可以創建一個已排序的對象數組，以表示相關數組項的每條記錄。 排序后，您可以獲取第一條或最后一條記錄以獲取最舊或最新的記錄。 請參見下面的示例。

const myArray = [
  {
    itemA: {
      name: "Joe Blow",
      date: "Mon Jan 31 2016 00:00:00 GMT-0700 (PDT)"
    },
    itemC: {
      name: "John Smith",
      date: "Sat Apr 29 2016 00:00:00 GMT-0700 (PDT)"
    },
    itemB: {
      name: "Sam Snead",
      date: "Sun March 30 2016 00:00:00 GMT-0700 (PDT)"
    }
  }
];

const sortedEntries = myArray.map((entry) => {
  const records = Object.values(entry);
  const sortedRecords = records.sort(function (prev, next) {
    return new Date(prev.date) < new Date(next.date) ? -1 : 1;
  });
  return sortedRecords;
});

// the array with records for each entry now sorted as an array from oldest to most recent date
console.log("sorted entries: ", sortedEntries);

// for example purposes, accessing your array by index, assuming you had more than 1 item in the array
const i = 0;

// get the record with most recent date for this array item
console.log(
  "most recent record for example entry is: ",
  sortedEntries[i][sortedEntries[i].length - 1]
);

https://codesandbox.io/s/festive-shadow-s36cf3

Answer 4

這個片段應該可以幫助你：

const myArray = [
  {
    itemA: {
      name: "Joe Blow",
      date: "Mon Jan 31 2016 00:00:00 GMT-0700 (PDT)"
    },
    itemC: {
      name: "John Smith",
      date: "Sat Apr 29 2016 00:00:00 GMT-0700 (PDT)"
    },
    itemB: {
      name: "Sam Snead",
      date: "Sun March 30 2016 00:00:00 GMT-0700 (PDT)"
    }
  }
];

const sortedArray = myArray.map(entry => {
  let tmpObj = {};
  let tmpSorted =  Object.keys(entry).sort((prev, next) => {
    return Date.parse(entry[next]?.date) - Date.parse(entry[prev]?.date);
  });

  tmpSorted.forEach(e => {
    tmpObj[e] = entry[e];
  })

  return tmpObj;
});


console.log(sortedArray);