数据类型
先声明一些变量
var arr = [1,2,3];
var obj = {};var a = function(){};
var b;
var c = 1+"a";
var d = "hello" * 3;
var f = null;
console.log(typeof RegExp) //function
console.log(typeof Date) //function
console.log(typeof arr) //object
console.log(typeof a) //function
console.log(typeof b) //undefined 定义但是未赋值
console.log(typeof c) //string
console.log(d) //NaN
console.log(typeof d) //number
console.log(typeof e) //undefined 未定义
// console.log(e) //e is not defined
console.log(typeof f) //object 空对象
console.log(typeof NaN); //number
console.log(null == undefined) //true
console.log(null === undefined) //false
console.log(NaN == NaN) //false NaN不等于任何值,连他本身也不等于
console.log(3+2+"a"); //5a
console.log("a"+2+3); //a23
console.log("你好,\n今天去那玩呀");
console.log("") //空字符串
console.log(" ") //空格字符串
// 原始数据类型 string number boolean undefined null
// 复合数据类型 object function