javaScript startsWith方法给出错误

Question

I am getting an error when filtering an array with startsWith method.

Error: Cannot read property startsWith of undefined

Here is my array:

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

i was expecting to have all the records those start with 'ACCESS'.

How to apply startsWith method on multiple objects having different properties within same array?

Answer 1

您需要检查Keyword属性是否首先存在：

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

Answer 2

You have plenty of objects that don't have the KeyWord property, so you have to account for those cases too:

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

Or, if the KeyWord property can potentially be of a type other than string:

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

Answer 3

there are some objects which does not have keyword . First check of its existence.

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