<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Typeof</title>
<script>
//对象不存在时返回null
//变量未被赋值是undefined
var test1 = "abcdef";
var test2 = 123;
var test3 = true;
var test4 = {};
var test5 = [];
var test6;
var test7 = {"abcdef": 123};
var test8 = ["abac", 123];
function test9(){return "avc"};
var test10 = null;
console.log(typeof test10)
//NaN是无法表示的数值,无法自身比较NaN != NaN, NaN与任何东西都不相等
//判断NaN,任何不是数字的值传给isNaN返回的结果都是true
var myNum;
if (isNaN(myNum)){
myNum = 0;
}
alert(myNum);
//Infinity指的是超过数据上限或这下限的值
if (99 == "99"){
console.log("A number equals a string");
} else {
console.log("No way a number equals a strings");
}
</script>
</head>
<body>
</body>
</html>
