使用TypeScript的時(shí)候，一定會(huì)遇到interface 和 type aliases 的比較。
官方有兩句話Because [an ideal property of software is being open to extension](https://en.wikipedia.org/wiki/Open/closed_principle), you should always use an interface over a type alias if possible.On the other hand, if you can’t express some shape with an interface and you need to use a union or tuple type, type aliases are usually the way to go，就是要我們一般情況下使用interface，當(dāng)interface不能滿足我們的需求時(shí)，使用type。
下面通過(guò)一些例子來(lái)比較兩者的異同

1. Objects / Functions

兩者都可以用來(lái)描述對(duì)象或函數(shù)，但是語(yǔ)法不同。

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. Other Types

與interface不同，type也可以用于其他類(lèi)型，例如原始類(lèi)型、聯(lián)合類(lèi)型、元祖類(lèi)型。

// primitive
type Name = string;

// object
type PartialPointX = { x: number; };
type PartialPointY = { y: number; };

// union
type PartialPoint = PartialPointX | PartialPointY;

// tuple
type Data = [number, string];

3. Extend 繼承

兩者都可以被繼承，但是同樣的，語(yǔ)法不同。

• interface extends interface

interface PartialPointX { x: number; }
interface Point extends PartialPointX { y: number; }

• type alias extends type alias

type PartialPointX = { x: number; };
type Point = PartialPointX & { y: number; };

• interface extends type alias

type PartialPointX = { x: number; };
interface Point extends PartialPointX { y: number; }

• type alias extends interface

interface PartialPointX { x: number; }
type Point = PartialPointX & { y: number; };

4. Implements 實(shí)現(xiàn)

一個(gè)class對(duì)于interface和type alias的實(shí)現(xiàn)是一樣的。但是，class和interface被認(rèn)為是靜態(tài)藍(lán)圖(static blueprints)，因此，他們不能 Implements / extend 聯(lián)合類(lèi)型的 type alias

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

class SomePoint implements Point {
    x: 1;
    y: 2;
}

type Point2 = {
    x: number;
    y: number;
};

class SomePoint2 implements Point2 {
    x: 1;
    y: 2;
}

type PartialPoint = { x: number; } | { y: number; };
// ? A class can only implement an object type or intersection of object types with statically known members.t
class SomePartialPoint implements PartialPoint {
    x: 1;
    y: 2;
}

4. Declaration Merging (聲明合并)

// These two declarations become:
// interface Point { x: number; y: number; }
interface Point { x: number; }
interface Point { y: number; }

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

【更多】https://www.typescriptlang.org/docs/handbook/advanced-types.html

【參考】typescript-interfaces-vs-types