2 questions on propagating 'direction' and 'writing-mode' from body to root

window.getComputedStyle(document.body)).direction == not available or not supported

window.getComputedStyle(document.body).not available or not supported

window.getComputedStyle(document.documentElement).direction == not available or not supported

window.getComputedStyle(document.documentElement).not available or not supported