JS - Testing code that uses an IntersectionObserver

Question

I have a (rather poorly written) javascript component in my application that handles infinite scroll pagination, and i\'m trying to rewrite it to use the IntersectionO

Answer 1

Had a similar stack issue as @Kevin Brotcke, except using their solution resulted in a further TypeScript error:

Function expression, which lacks return-type annotation, implicitly has an 'any' return type.

Here's a tweaked solution that worked for me:

beforeEach(() => {
    // IntersectionObserver isn't available in test environment
    const mockIntersectionObserver = jest.fn()
    mockIntersectionObserver.mockReturnValue({
      observe: jest.fn().mockReturnValue(null),
      unobserve: jest.fn().mockReturnValue(null),
      disconnect: jest.fn().mockReturnValue(null)
    })
    window.IntersectionObserver = mockIntersectionObserver
  })