JS基礎知識整理(持續更新......
阿新 • • 發佈:2018-11-03
資料型別
先宣告一些變數
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 arr) //object
console.log(typeof a) //function
console.log(typeof b) //undefined 定義但是未賦值
console.log(typeof c) //string
console.log(typeof d) //number
console.log(typeof e) //undefined 未定義
// console.log(e) //e is not defined
console.log(typeof f) //object 空物件
console.log(null == undefined) //true
console.log(null === undefined) //false
console.log(NaN == NaN) //false NaN不等於任何值,連他本身也不等於
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("") //空字串
console.log(" ") //空格字串
// 原始資料型別 string number boolean undefined null
// 複合資料型別 object function