typeScript之数据类型

javaScript数据类型可分为两大类: 1:基本数据类型:number,string,boolean,undefined,null,symbol 2.引用类型:object(Array,Function,Data)

1.1:number类型

let age:number = 18

1.2:string类型

let firstName:string = "chance"

1.3:boolean类型

let isDone:boolean = false

1.4:undefined类型

let u:undefined = undefined

1.5:null类型

let n:null = null

  注意:undefined和null是所有类型的子类型, undefined类型变量可以赋值给任何类型的变量  

let num:number = undefined
let nums:boolean = undefined
let  first:string = undefined
let c:null = undefined