Need fullscreen API

How to control fullscreen by player API?

When I make fullscreen with [iframe], it goes to fullscreen.
like

const dv= document.getElementById('cloudflare');
dv.requestFullscreen();

BUT after it, when try to cancel fullscreen with button of player, It’s not working.
I guess fullscreen-button works with [video] tag which I can not access as it’s inside of iframe.
So please make a API for fullscreen or fullscreen-button work with [iframe].