js 页面全屏，退出全屏, fullScreen

项目有个需求，当点击打开一个新页面的时候需要该页面全屏（类似F11键功能），查找之后发现没办法直接用js来触发全屏，只能通过用户鼠标、键盘等事件中才能触发，即“对于一些非用户事件，比如onload、timeout等之类的事件中调用requestFullScreen是无法生效的，出于安全性考虑必须在用户事件中调用，比如鼠标、键盘等操作”。
文档全屏的方法本身是作用在body或documentElement上的，也可以作用的元素本身上，其他元素如CANVAS、VIDEO，之类的也可以发起全屏请求。

作用在document的全屏代码

function fullScreen(){
  var docElm = document.documentElement; 
  if (docElm.requestFullscreen) {  
      docElm.requestFullscreen();  
  } else if (docElm.mozRequestFullScreen) {
      docElm.mozRequestFullScreen();  
  } else if (docElm.webkitRequestFullScreen) {
      docElm.webkitRequestFullScreen();  
  } else if (elem.msRequestFullscreen) {
    elem.msRequestFullscreen();
  }
}

作用在document的关闭全屏代码

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

基于元素全屏的代码

    <div id="content" style="width:500px;height:500px;background:red;">
        这是被全屏的元素
        <button id='btn'>全屏button>
        <button id="closeBtn">退出全屏button>  
    div> 

//js code
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}");  
        }  
    }  
}    
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 btn = document.getElementById('btn');  
var content = document.getElementById('content');   //被全屏显示的元素
btn.onclick = function(){  
    fullScreen(content);  
}  
var closeBtn = document.getElementById('closeBtn');  
closeBtn.onclick = function(){  
    exitFullScreen();  
}