// https://stackoverflow.com/a/23971798
window.addEventListener('click', () => {
    toggleFullScreen()
})

function isFullScreen() {
    return (document.fullScreenElement && document.fullScreenElement !== null)
            || document.mozFullScreen
            || document.webkitIsFullScreen
}

function requestFullScreen(element) {
    if (element.requestFullscreen)
        element.requestFullscreen()
    else if (element.msRequestFullscreen)
        element.msRequestFullscreen()
    else if (element.mozRequestFullScreen)
        element.mozRequestFullScreen()
    else if (element.webkitRequestFullscreen)
        element.webkitRequestFullscreen()
}

function exitFullScreen() {
    if (document.exitFullscreen)
        document.exitFullscreen()
    else if (document.msExitFullscreen)
        document.msExitFullscreen()
    else if (document.mozCancelFullScreen)
        document.mozCancelFullScreen()
    else if (document.webkitExitFullscreen)
        document.webkitExitFullscreen()
}

function toggleFullScreen(element) {
    if (isFullScreen()) exitFullScreen()
    else requestFullScreen(element || document.documentElement)
}