3）嵌套函数
例 3.3.1
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8"/>
</head>
<script>
function outerFun(){
var i = 0;
function innerFun(){
document.write(i);
}
innerFun();
}
outerFun();
/*here you can not call innerFun(), because it is inside another function outerFun, so it will cause error.*/
innerFun();
document.write("马克-to-win");
</script>
文章转载自：https://blog.csdn.net/qq_44594249/article/details/99978852