如何实现加载网页时（body onload），网页自动全屏实现F11的效果

如何实现加载网页时（body onload），网页自动全屏实现F11的效果。
如下通过点击按钮可以实现，如何改成页面加载自动执行全屏？


```html

<html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>测试全屏title>

 
head>
<body id="content">

 <button id='btn' >全屏按钮button> 

<div id="quite" class="btns">退出全屏div> 
div>


 <script type="text/javascript">

var btn = document.getElementById('btn'); 
  var content = document.getElementById('content'); 
  btn.onclick = function(){ 
   console.log(content);
fullScreen(content); 
  }  
  
  var quite = document.getElementById('quite'); 
  quite.onclick = function(){
   exitFullScreen(); 
  }


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}"); 
}
}
}
 script>
body>
html>

```

如下：


 
<html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>测试全屏</title>
 
 
</head>
<body id="content">
 
 <button id='btn' >全屏按钮</button> 
 
<div id="quite" class="btns">退出全屏</div> 
</div>
 
 
 <script type="text/javascript">

window.onload = function() {
  fullScreen(document.documentElement); 
}
 
var btn = document.getElementById('btn'); 
  var content = document.getElementById('content'); 
  btn.onclick = function(){ 
   console.log(content);
fullScreen(content); 
  }  
  
  var quite = document.getElementById('quite'); 
  quite.onclick = function(){
   exitFullScreen(); 
  }
 
 
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}"); 
}
}
}
 </script>
</body>
</html>

window.onload=function（）｛要执行的代码｝