《初入typescript》

点击这里编写typescript

声明类型

type Name = string
const str: Name = 'frank'

将string属性给Name str属于Name类型，也就有string属性

type Id = string | number
const id1:Id = '123'
const id1:Id = 123

既有string属性，又有number属性

 type A = {
     t:'a';
     specialForA:string
 }
  type B = {
     tt:'b';
     specialForb:number
 }
 type Target1 = A | B
 const c1:Target1 ={
     t:'a',
     specialForA:'123'
 }

c1的属性整体要么A，要么B，前提要有相同的t,

同名属性内容没法重合，就不能用&

 type A = {
     ta:'a';
     specialForA:string
 }
  type B = {
     tb:'b';
     specialForb:number
 }
 type Target1 = A & B
 const c1:Target1 ={
     ta:'a',
     tb:'b',
     specialForA:'123',
     specialForb:123
 }

type Dog = string
type Cat = 'Cat'
interface User {
    readonly id:number | string
    name:string
    age?: number
}
interface UserWithDog extends User{
    dog:Dog
}
const  u1:UserWithDog={
    name: 'jack',
    id:1,
    dog:'hi'
}
interface UserWithPet<T> extends User{
   pet:T
}
const u2:UserWithPet<Cat> = {
    id:1,
    name:'tt',
    age:3,
    pet:'Cat'
}

interface只能用来写对象，