function openFullScreen() {
    var doc = document.documentElement;
    if (doc.requestFullscreen) {
        doc.requestFullscreen();
    } else if (doc.msRequestFullscreen) {
        doc.msRequestFullscreen(); //早期IE浏览器
    } else if (doc.webkitRequestFullScreen) {
        doc.webkitRequestFullScreen(); //早期Chrome浏览器
    } else if (doc.mozRequestFullScreen) {
        doc.mozRequestFullScreen();  //早期火狐浏览器
    }
}

function exitFullScreen() {
    var doc = document;
    if(doc.exitFullscreen) {
        doc.exitFullscreen();
    } else if(doc.msExitFullscreen) {
        doc.msExitFullscreen(); //早期IE浏览器
    } else if(doc.webkitExitFullscreen) {
        doc.webkitExitFullscreen(); //早期Chrome浏览器
    } else if(doc.mozCancelFullScreen) {
        doc.mozCancelFullScreen(); //早期火狐浏览器
    }
}

function isFullScreen(){
    return !!(document.fullscreenElement || document.msFullScreenElement || document.webkitFullScreenElement || document.mozFullScreenElement);
}