No type info available except "isEnabled"

[foobardevpro]

Any property besides isEnabled gives an error like this (same for request, on, exit, etc):

TS2339: Property 'isFullscreen' does not exist on type 'Screenfull | { isEnabled: false; }'.
  Property 'isFullscreen' does not exist on type '{ isEnabled: false; }'.

Issue is solved if I change:
https://github.com/sindresorhus/screenfull.js/blob/b2a50cc4d1554ef62530a4cae973096a96921c93/src/screenfull.d.ts#L157
to:

declare const screenfull: screenfull.Screenfull;

[sindresorhus]

Per readme, you have to guard the usage:

if (screenfull.isEnabled) {
	screenfull.request();
}

[beac0n]

Per readme, you have to guard the usage:

if (screenfull.isEnabled) {
	screenfull.request();
}

That is some smart typing. Really neat. I learned something today :-).

I'll explain it to anyone who comes across this issue and scratches their head, like I have:

declare const screenfull: screenfull.Screenfull | {isEnabled: false};

This type definition prevents users from using screenfull.isFullscreen or any other property of screenfull.Screenfull, if screnfull.isEnabled isn't checked first.

It works, because if the user uses screenfull.isFullscreen as is, typescript tries to find isFullscreen in the type {isEnabled: false}, which fails, because isFullscreen doesn't exist on {isEnabled: false}.

If the user checks isEnabled for true first, typescript deduces that the type can not be {isEnabled: false} and uses the type screenfull.Screenfull instead.

[loicraux]

If you don't want to wrap all your screenfull API calls with an if guard statement, you call also use an assertion function (provided that you use TS >= 3.7) :

function assert(condition: boolean, message?: string): asserts condition {
    if (!condition) {
        // eslint-disable-next-line no-console
        console.trace();
        throw new Error(message);
    }
}

// Some button in your DOM to switch to fullscreen :
const switchToFullScreenButton: HTMLButtonElement = .... ;

switchToFullScreenButton.addEventListener('click', handleClickOnFullscreenButton);
switchToFullScreenButton.disabled = !screenfull.isEnabled;

function handleClickOnFullscreenButton(): void {
    // Here you expect screenfull.isEnabled to be true, so you can assert :
    assert(screenfull.isEnabled);

    // In the rest of the code of this handler, you can use the complete screenfull API,
    if (screenfull.isFullscreen) {
        screenfull.exit();
    } else {
        screenfull.request(someElement);
    }
}