【TypeScript】一、基础类型

1. 字符串
   let str:string = '123456'
2. 数字
   let num: number = Infinity
3. bool
   let b:boolean = Boolean(0)
4. void
   let v:void = undefined
5. any
   let n:any = null
6. function

function fn(): void {
    // return void || return || 不写
}

7. null & undefined

let u1:null = null
let v1:undefined = undefined