const area = await new Promise((resolve) => {
    window.requestAnimationFrame(() => {
        const { offsetWidth, offsetHeight } = someElement;
        resolve(offsetWidth * offsetHeight);
    });
});

const area = await asyncRaf(() => {
    const { offsetWidth, offsetHeight } = someElement;
    return offsetWidth * offsetHeight;
});

// All callbacks will be execute inside `requestAnimationFrame()`

asyncRaf(() => {
	// get some properties that causes page reflow
	const { offsetWidth, offsetHeight } = someElement;
	// return a value to be resolved.
	return offsetWidth * offsetHeight;
});

// OR resolve it yourself
asyncRaf((resolve) => {
	// get some properties that causes page reflow
	const { offsetWidth, offsetHeight } = someElement;
	// resolve the value.
	resolve(offsetWidth * offsetHeight);
});

// OR use async callback
asyncRaf(async () => {
	// get some properties that causes page reflow
	const { offsetWidth, offsetHeight } = someElement;
	const area = await calculateElementArea(offsetWidth, offsetHeight);
	return area;
});