2.全屏

function fullScreen(el) {

    var rfs = el.requestFullScreen || el.webkitRequestFullScreen || el.mozRequestFullScreen || el.msRequestFullScreen, 

        wscript; 

    if(typeof rfs != "undefined" && rfs) { 

        rfs.call(el); 

        return; 

    }   

    if(typeof window.ActiveXObject != "undefined") { 

        wscript = new ActiveXObject("WScript.Shell"); 

        if(wscript) { 

            wscript.SendKeys("{F11}"); 

        } 

    } 

}

var btn = document.getElementById('fullscreenshow'); // 点击按钮

var content = document.getElementById('fullbody');  //被全屏显示的元素

    btn.onclick = function(){ 

    fullScreen(content);

}

3.退出全屏

function exitFullScreen(el) {

    var el= document, 

        cfs = el.cancelFullScreen || el.webkitCancelFullScreen || el.mozCancelFullScreen || el.exitFullScreen, 

        wscript;   

    if (typeof cfs != "undefined" && cfs) { 

      cfs.call(el); 

      return; 

    }   

    if (typeof window.ActiveXObject != "undefined") { 

        wscript = new ActiveXObject("WScript.Shell"); 

        if (wscript != null) { 

            wscript.SendKeys("{F11}"); 

        } 

  } 

}

var closeBtn = document.getElementById('backfullpage'); 

closeBtn.onclick = function(){ 

    exitFullScreen();

}