type定义
type作用就是给类型起一个新名字,支持基本类型、联合类型、元祖及其它任何你需要的手写类型,常用于联合类型
type test = number; //基本类型
let num: test = 10;
type userOjb = {name:string} // 对象
type getName = ()=>string // 函数
type data = [number,string] // 元组
type numOrFun = Second | getName // 联合类型
interface只能表示function,object和class类型
interface A{name:string;
add:()=>void;
}
interface B{():void}
type和interface的区别
1、和接口一样,用来描述对象或函数的类型
type User = {
name: string
age: number
};
type SetUser = (name: string, age: number)=>void;
2、扩展和实现(extends & implement)
interface可以扩展,type可以通过交叉实现interface的extends行为
interface可以extends type,同时type也可以与interface类型交叉
interface Name {
name: string;
}
interface User extends Name {
age: number
}
let stu:User = {name: 'wang', age: 10}
//interface的扩展可以通过type交叉(&)类型实现
type Name = {
name: string;
}
type User = Name & {age: number}
let stu:User={name: 'wang', age: 18}
//interface 扩展 type
type Name = {
name: string;
}
interface User extends Name {
age: number;
}
let stu:User={name: 'wang', age: 89}
//type与interface交叉
interface Name {
name: string;
}
type User = Name & {
age: number;
}
let stu:User={name:'wang', age: 18}
3、映射类型
type Keys = "name" | "sex"
type DuKey = {
[Key in Keys]: string //类似 for ... in
}
let stu: Dukey = {
name: 'wang',
sex: 'man'
}
4、interface可以合并同名接口,type不可以
interface A{name:string}
interface A{age:number}
var x:A={name:'xx',age:20}
5.、nterface可以继承interface,继承type,使用extends关键字,type也可继承type,也可继承interface,使用&
interface A{name:string}
interface B extends A{age:number}
type C={sex:string}
interface D extends C{name:string}
type E={name:string}&C
type F ={age:number}&A
6、还有类可以实现接口,也可以实现type
interface A{name:string;add:()=>void}
type B={age:number,add:()=>void}
class C implements A{
name:'xx'
add(){console.log('类实现接口')}
}
class D implements B{
age:20
add(){console.log('类实现type')}
}