Currently, I am immersing myself in the Angular - Testing documentation. While going through the section on testing asynchronous services (specifically HTTP services), I came across a class constructor containing an <any> right before the passed argument. The exact line reads:
heroService = new HeroService(<any> httpClientSpy);I understand that in Typescript, using any denotes a type as "any." But why are the angle brackets (<...>) used in this context? And what purpose does typing in front of the argument serve? Is it utilized for type parsing?
The code snippet extracted from the documentation is as follows:
let httpClientSpy: { get: jasmine.Spy };
let heroService: HeroService;
beforeEach(() => {
// TODO: spy on other methods too
httpClientSpy = jasmine.createSpyObj('HttpClient', ['get']);
heroService = new HeroService(<any> httpClientSpy);
});
it('should return expected heroes (HttpClient called once)', () => {
const expectedHeroes: Hero[] =
[{ id: 1, name: 'A' }, { id: 2, name: 'B' }];
httpClientSpy.get.and.returnValue(asyncData(expectedHeroes));
heroService.getHeroes().subscribe(
heroes => expect(heroes).toEqual(expectedHeroes, 'expected heroes'),
fail
);
expect(httpClientSpy.get.calls.count()).toBe(1, 'one call');
});
it('should return an error when the server returns a 404', () => {
const errorResponse = new HttpErrorResponse({
error: 'test 404 error',
status: 404, statusText: 'Not Found'
});
httpClientSpy.get.and.returnValue(asyncError(errorResponse));
heroService.getHeroes().subscribe(
heroes => fail('expected an error, not heroes'),
error => expect(error.message).toContain('test 404 error')
);
});