supportsIO

1/**
2 * Checks if the current environment supports IntersectionObserver.
3 *
4 * @returns True if supported, false otherwise.
5 */
6export function supportsIO(): boolean {
7  return typeof window !== 'undefined' &&
8    'IntersectionObserver' in window &&
9    'IntersectionObserverEntry' in window &&
10    'intersectionRatio' in IntersectionObserverEntry.prototype;
11}

1const originalWindow = globalThis.window;
2
3afterEach(() => {
4  globalThis.window = originalWindow;
5});
6
7test('returns true if IntersectionObserver is supported', () => {
8  globalThis.window = {
9    IntersectionObserver: function () {},
10    IntersectionObserverEntry: function () {},
11  } as any;
12  (globalThis.window.IntersectionObserverEntry.prototype as any) = {
13    intersectionRatio: 0,
14  };
15
16  expect(supportsIO()).toBe(true);
17});
18
19test('returns false if IntersectionObserver is missing', () => {
20  globalThis.window = {
21    IntersectionObserverEntry: function () {},
22  } as any;
23  (globalThis.window.IntersectionObserverEntry.prototype as any) = {
24    intersectionRatio: 0,
25  };
26
27  expect(supportsIO()).toBe(false);
28});
29
30test('returns false if IntersectionObserverEntry is missing', () => {
31  globalThis.window = {
32    IntersectionObserver: function () {},
33  } as any;
34
35  expect(supportsIO()).toBe(false);
36});
37
38test('returns false if not in a browser environment', () => {
39  // @ts-expect-error
40  delete globalThis.window;
41  expect(supportsIO()).toBe(false);
42});