TS中interface
(接口)和type
(类型别名)有许多相似之处:
- 理论开发中两者都能够用来束缚变量的类型
- 两者都能够扩大
- 接口和类型别名不是互斥的,接口能够扩大类型别名,反之亦然
上面次要来看下区别
1、申明形式不同
interface Point {
x: number;
y: number;
}
interface SetPoint {
(x: number, y: number): void;
}
type Point = {
x: number;
y: number;
};
type SetPoint = (x: number, y: number) => void;
2、类型别名(type
)还能够用于其余类型,如根本类型(原始值)、联结类型、元组
// primitive
type Name = string;
// union
type PartialPoint = PartialPointX | PartialPointY;
// tuple
type Data = [number, string];
// dom
let div = document.createElement('div');
type B = typeof div;
3、扩大时语法不同,且interface
无奈扩大联结类型的type
interface PartialPointX { x: number; }
interface Point extends PartialPointX { y: number; }
type PartialPointX = { x: number; };
type Point = PartialPointX & { y: number; };
type PartialPoint = { x: number; } | { y: number; };
// 报错:无奈实现一个联结类型的type
// class SomePartialPoint implements PartialPoint {
// x: 1;
// y: 2;
// }
4、interface
能够定义屡次,并将被视为单个接口(合并所有申明的成员);type
不能够
interface Point { x: number; }
interface Point { y: number; }
const point: Point = { x: 1, y: 2 };
5、interfac能够extends
class,class也能够implements
interface
class Point {
x: number;
y: number;
}
interface Point3d extends Point {
z: number;
}
interface Foo {
name: string;
age: number;
sayHello(): void;
}
class Bar implements Foo {
name: string;
age: number;
sayHello(): void {
console.log('Hello');
}
}
6、type
反对计算属性,生成映射类型,interface
不能够
type
能应用in
关键字生成映射类型,但interface
不行- 语法与索引签名的语法类型,外部应用了
for .. in
type Keys = "firstname" | "surname"
type DudeType = {
[key in Keys]: string
}
const test: DudeType = {
firstname: "Pawel",
surname: "Grzybek"
}
// 报错
//interface DudeType2 {
// [key in keys]: string
//}
总结:我平时开发中,习惯在一个module下新建一个公共文件interface.ts
,专门export各种interface,用于束缚以后module业务代码中各种变量的类型和取值范畴;如果独自某个组件中的变量取值范畴比拟非凡,那就在其组件业务代码中用type束缚下