How Blazor interop does work (when you return the promises)

gistfile1.txt

window.IsUrlCached = (url) => {
	return caches.open(CACHE_NAME)
		.then((cache) => {
				return cache.match(url)
					.then((response) => {
						if (typeof response !== 'undefined')
							return true;
						else
							return false;
					});
			}
	);
}

// from C#:
var isCached = await _jsRuntime.InvokeAsync<bool>("IsUrlCached", url);
// original version failed because I wasn't returning the promises in the chain