js全屏、退出全屏、判断是否处于全屏状态

function showFullScreen(){
    lastFullScreenFlag=true;
    if (!document.fullscreenElement &&!document.mozFullScreenElement 
    && !document.webkitFullscreenElement &&!document.msFullscreenElement) { 
        if (document.documentElement.requestFullscreen) {
            document.documentElement.requestFullscreen();
        } else if (document.documentElement.msRequestFullscreen) {
            document.documentElement.msRequestFullscreen();
        } else if (document.documentElement.mozRequestFullScreen) {
            document.documentElement.mozRequestFullScreen();
        } else if (document.documentElement.webkitRequestFullscreen) {
            document.documentElement.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);
        }
    }
}

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

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