javascript - 类型错误 : Cannot set property 'xxx' of undefined

Question

我是 typescript 新手，我编写了这段代码来用 Jest 测试方法，

describe('book', () => {

    let hostelClient: HostelClient;


    it('should book', async () => {

        hostelClient.getRequestByIdAsync = jest.fn().mockReturnValue({});

        // Assert
        let exceptionThrown = false;
        expect(exceptionThrown).toBe(false);
     });

});

但是我有这个错误:

 TypeError: Cannot set property 'getRequestByIdAsync' of undefined

和

@Service()
export class HostelClient  {

    constructor() {
        throw new Error('not allowed);
    }
..
}

Answer 1

请尝试这个:

describe('book', () => {

let hostelClient: HostelClient = new HostelClient();


it('should book', async () => {

    hostelClient.getRequestByIdAsync = jest.fn().mockReturnValue({});

    // Assert
    let exceptionThrown = false;
    expect(exceptionThrown).toBe(false);
 });
});

在您的示例中，您定义变量，但没有将该变量实例化为新的 hostelClient。