全屏了却判断为未全屏（已解决)

function isFullScreen () {
    var isFull = false;
    if (document.fullscreenEnabled || document.msFullscreenEnabled ) {
        isFull = window.fullScreen || document.webkitIsFullScreen;
        if (isFull === undefined) {
            isFull = false;
        }
    }
    return isFull

function isFullScreen () {
  return 
  document.
  isFullScreen || 
  document.
  mozIsFullScreen || 
  document.
  webkitIsFullScre
}

function isFullscreen () {
      const screen = window.screen
      const body = document.body.getBoundingClientRect()
      return screen.height === body.height && screen.width === body.width
}