原始类型之typeof运算符

typeof

返回一个用来表示表达式的数据类型的字符串。

typeof[()expression[]] ;

expression 参数是需要查找类型信息的任意表达式。

说明

typeof 运算符把类型信息当作字符串返回。typeof 返回值有六种可能： "number," "string," "boolean," "object," "function," 和 "undefined."

typeof 语法中的圆括号是可选项。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>原始类型之typeof运算符</title>

<script type="text/javascript">
var s='s';
var i=12;
var t=true;
var nu=null;
var undi;
alert(typeof(s)+" "+typeof(i)+" "+typeof(t)+" "+typeof(nu)+" "+typeof(undi));
//output string number boolean object undefined
</script>
</head>

<body>
</body>
</html>