Types_vs_Interfaces.md

Types vs Interfaces

相同点

1. 两者都可用来表达 Objects / Functions, 不过它们语法不同。

Interface:

interface Point0 {
  x: number;
  y: number;
}

interface SetPoint0 {
  (x: number, y: number): void
}

Type:

type Point1 = {
  x: number;
  y: number;
}

type SetPoint1 = (x: number, b: number) => void

2. 两者都可以继承自 Interface 或者 Type。

继承自 Interface:

interface PartialPointX0 { x: number }
interface Point extends PartialPointX0 { y: number }

interface PartialPointX3 { x: number }
type PointX1 = PartialPointX3 & { y: number }

继承自 Type:

type PartialPointX1 = { x: number }
type PointX1 = PartialPointX1 & { y: number }

type PartialPointX2 = { x: number }
interface Point extends PartialPointX2 { y: number }

不同点

1. Type 可用来定义声明 primitives, unions 以及 tuples 类型。

// primitive
type Name = string;

// union
type Point = string | number

// tuple
type Data = [string, number]

2. Interface 可声明多次, 多次声明的类型会进行合并。Type 则只能声明一次。

interface Point { x: number }
interface Point { y: number }

const point: Point = { x: 1, y: 2 }

Types_vs_Interfaces