js控制全屏和取消全屏

function fullScreen(docElm) {
    if (window.isFullScreen) {
        return;
    }
    // const docElm = document.documentElement
    if (docElm.requestFullscreen) {
        docElm.requestFullscreen();
    } else if (docElm.mozRequestFullScreen) {
        docElm.mozRequestFullScreen();
    } else if (docElm.webkitRequestFullScreen) {
        docElm.webkitRequestFullScreen();
    } else if (docElm.msRequestFullscreen) {
        docElm.msRequestFullscreen();
    }
    window.isFullScreen = true;
}

function cancelFullScreen() {
    if (!window.isFullScreen) {
        return;
    }
    if (document.exitFullscreen) {
        document.exitFullscreen();
    } else if (document.mozCancelFullScreen) {
        document.mozCancelFullScreen();
    } else if (document.webkitCancelFullScreen) {
        document.webkitCancelFullScreen();
    } else if (document.msCancelFullScreenn) {
        document.msCancelFullScreen();
    }
    window.isFullScreen = false;
}