先放個官方 Web API 接口 链接：全屏 API

网上基本都是这种：

//全屏功能
    document.getElementById("ck_buts").onclick = function() {
        var elem = document.getElementById("dashboard_id");
        elem.style.width = "100%";
        elem.style.height = "100%";
        elem.style.overflowY = "scroll";
        requestFullScreen(elem); // 某个页面元素
        //requestFullScreen(document.documentElement); // 整个网页
    };

    function requestFullScreen(element) {
            // 判断各种浏览器，找到正确的方法
            var requestMethod = element.requestFullScreen || //W3C
                element.webkitRequestFullScreen || //FireFox
                element.mozRequestFullScreen || //Chrome等
                element.msRequestFullScreen; //IE11
            if (requestMethod) {
                requestMethod.call(element);
            } else if (typeof window.ActiveXObject !== "undefined") { //for Internet Explorer
                var wscript = new ActiveXObject("WScript.Shell");
                if (wscript !== null) {
                    wscript.SendKeys("{F11}");
                }
            }
        }
        //退出全屏 判断浏览器种类

    function exitFull() {
        // 判断各种浏览器，找到正确的方法
        var exitMethod = document.exitFullscreen || //W3C
            document.mozCancelFullScreen || //FireFox
            document.webkitExitFullscreen || //Chrome等
            document.webkitExitFullscreen; //IE11
        if (exitMethod) {
            exitMethod.call(document);
        } else if (typeof window.ActiveXObject !== "undefined") { //for Internet Explorer
            var wscript = new ActiveXObject("WScript.Shell");
            if (wscript !== null) {
                wscript.SendKeys("{F11}");
            }
        }

    }

 监听退出全屏事件：

//监听退出全屏事件
    window.onresize = function() {
        if (!checkFull()) {
            //要执行的动作
            $("#dashboard_id").removeClass('expand').addClass('contract');//这里捡个懒，直接用JQ来改className
        }
    }
    function checkFull() {
        var isFull = document.fullscreenEnabled || window.fullScreen || document.webkitIsFullScreen || document.msFullscreenEnabled;
        //to fix : false || undefined == undefined
        if (isFull === undefined) {isFull = false;}
        return isFull;
    }

我试了试，无法正常监听退出全屏事件（Esc、F11）。

注：全屏状态无法监听键盘按键事件。

故：采用监听onresize ，onresize 事件会在窗口或框架被调整大小时发生。

window.onresize = function() {
    if (document.fullscreenElement) {
        console.log('进入全屏')
    } else {
        // TODO...
        console.log('退出全屏')
    }
};

Ok！！！