javaScript startsWith方法給出錯誤

Question

使用startsWith方法過濾數組時出現錯誤。

錯誤：無法讀取未定義的屬性startsWith

這是我的數組：

let testdata = [
    {
      _id: "5d0876833827c2176cae90df",
      MobileNumber: "965XXXXXXX",
      Keyword: "ACCESSORIES",
      DateStamp: 1560835715501,
      id: "5d0876833827c2176cae90df"
    },
    {
      _id: "5d0876833827c2176cae90e0",
      MobileNumber: "965XXXXXXX",
      Keyword:
        "ACCESSORIES, ANNIVERSARY, BABY, BAGS, BATHING SUIT, BELTS, 
         BIRTHDAY, BIRTHDAY GIFT, BRAND, BRANDS, CHILDREN, CLOTHING, 

      DateStamp: 1560835715501,
      id: "5d0876833827c2176cae90e0"
    },
    {
      _id: "5d0876833827c2176cae90e1",
      MobileNumber: "965XXXXXXX",
      Keyword:
        "ACCESSORIES, ANNIVERSARY, BABY, BAGS, BATHING SUIT, BELTS, 
         BIRTHDAY, BIRTHDAY GIFT, BRAND, BRANDS, CHILDREN, CLOTHING, 
         COMFORT, DEALS, DISCOUNT, DRESS, DRESSES, EXCHANGE, FASHION, 
         GIFT, GIFT CARD, GLASSES, HAIR.",
        DateStamp: 1560835715501,
        id: "5d0876833827c2176cae90e1"
    },
    {
      _id: "5d08c7c79d70334824470fb4",
      Name: "JOHN",
      MobileNumber: "961XXXXXXX",
      AnotherNumber: "NULL",
      Email: "NULL",
      FamilyName: "SMITH",
      Gender: "M",
      DateStamp: 1560856519847,
      id: "5d08c7c79d70334824470fb4"
    },

    {
      _id: "5d08c7c79d70334824470fb6",
      Name: "ANTHONY",
      MobileNumber: "961XXXXXXX",
      AnotherNumber: "NULL",
      Email: "NULL",
      FamilyName: "JR",
      Gender: "M",

      DateStamp: 1560856519848,
      id: "5d08c7c79d70334824470fb6"
    },

    {
      _id: "5d0884ef3827c2176cb2a970",
      MobileNumber: "96170359896",
      PlateNumber: "NULL",
      CarModel: "NULL",
      CarType: "NULL",
      DateStamp: 1560839407029,
      id: "5d0884ef3827c2176cb2a970"
    },
    {
      _id: "5d0884ef3827c2176cb2a971",
      MobileNumber: "961XXXXXXXX",
      PlateNumber: "P293676",
      CarModel: "SEDAN",
      ProductionDateOfCar: 1483228800000,
      PurchaseDateOfCar: 1499281200000,
      CarType: "HONDA",
      DateStamp: 1560839407029,
      id: "5d0884ef3827c2176cb2a971"
    }
  ];

console.log(testdata.filter(d => d.Keyword.startsWith('ACCESS))); //getting error

我希望所有記錄都以“ ACCESS”開頭。

如何在同一數組中具有不同屬性的多個對象上應用startsWith方法？

Answer 1

您需要檢查Keyword屬性是否首先存在：

console.log(testdata.filter(d => d.Keyword && d.Keyword.startsWith('ACCESS')));

Answer 2

您有許多沒有KeyWord屬性的對象，因此您也必須考慮這些情況：

testdata.filter(d => d.KeyWord && d.Keyword.startsWith('ACCESS'));

或者，如果KeyWord屬性可能是字符串以外的其他類型：

testdata.filter(d => typeof d.KeyWord === 'string' && d.Keyword.startsWith('ACCESS'));

Answer 3

有些對象沒有keyword 。 首先檢查其存在。

console.log(testdata1.filter(d =>d.Keyword ? d.Keyword.startsWith('ACCESS') : false))