Object.keys（myObject）不返回打字稿中类的属性

Question

为什么这样做：

let provider = new Provider();
var keys = Object.keys(provider);
console.log(keys);

在以下情况下返回空数组

：

let provider = { Name: '', Surname: '' };
var keys = Object.keys(provider);
console.log(keys);

是否返回其中具有2个属性的数组？

这是我的Provider.ts：

export class Provider {
  public Id: string;
  public Name: string;
  public FriendlyName: string;
  public CompanyRegistrationNumber: string;
  public VatRegistrationNumber: string;
  public TfgUniqueReferenceNumber: string;
  public Since: Date;
  public Until: Date;
  public DefaultBillingDay: number;
  public DefaultProvisioningDay: number;
  public AllowsToProvisionProRata: boolean;
  public AllowsToBillProRata: boolean;
  public EmailAddress: string;
  public DateCreated: Date;
  public DateModified: Date;
  public UserCreated: string;
  public UserModified: string;
  public IsRetired: boolean;
  public ImageUrl: string;
  public ContactNumber1: ContactNumber;
  public ContactNumber2: ContactNumber;
  public PhysicalAddress: Address;
  public PostalAddress: Address;
  public FinancialSystemAccount: FinancialSystemAccount;
  public WholesaleProducts: Array<WholesaleProduct>;
  public ContactPeople: Array<ContactPerson>;
  public Batches: Array<Batch>;
  public BatchCandidates: Array<BatchCandidate>;
  public AllowableBatchTypes: Array<BatchType>;
}

Answer 1

除非初始化属性，否则实际上不会创建它们。您可以检查已交易的Provider.js文件并进行验证。这只是一种告诉编译器的方法，每当我们在Provider实例中使用时，都将强制使用那些预定义的类型。

在Typescript Playground

上对其进行测试

这堂课

class Provider {
  public Id: string;
  public Name: string;
  public FriendlyName: string;
  public CompanyRegistrationNumber: string;
  public VatRegistrationNumber: string;
  public TfgUniqueReferenceNumber: string;
  public InitializedProp: string = '';
}

被交易到：

var Provider = (function () {
    function Provider() {
        this.InitializedProp = '';
    }
    return Provider;
}());

您可以看到，仅InitializedProp被创建为经过转换的构造函数中的属性。