<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script>
/*undefined*/
alert(typeof a);
/*number*/
var b=12;
alert(typeof b);
var c='abc';
alert(typeof c);
var d=true;
alert(typeof d);
window.onload=function(){
var obtn=document.getElementById('div1');
alert(typeof obtn);
}
e=function(){
alert(abc);
}
alert(typeof e);
</script>
</head>
<body>
<div id="div1"></div>
</body>
</html>