JS tela completa
//creating a button and linking it to btnClicked()
document.onload=()=>{
let btn = document.createElement("button");
btn.textContent = 'Fulscreen!';
btn.addEventListener('click', btnClicked);
document.body.append(btn);
}
function btnClicked(){
document
.getElementById("%id of the element you want to fullscreen%")
.requestFullscreen();
}
//to exit fullscreen
document.exitFullscreen();
Witty Whale