typeof 运算符

	var arr = new Array();
	var myf = function(){};
	//typeof 后面如果是 表达式，必须加()
	alert("typeof 1 = " + typeof 1);//number	
	alert("typeof (\"1\" - 0) = " + typeof ("1"- 0));//number

	alert("typeof \"1\" = " + typeof "1");//string
	alert("typeof (1 + \"\") = " + typeof (1 + ""));//string

	alert("typeof (1==2) = " + typeof (1==2));//boolean
	alert("typeof(1==1) = " + typeof(1==1));//boolean
	
	alert("typeof [] = " + typeof []);//object
	alert("typeof null = " + typeof null);//object
	alert("typeof arr = " + typeof arr);//object

	alert("typeof myf = " + typeof myf);//function

	alert("typeof abc = " + typeof abc);//undefined