type 和 interface 的区别

type 可以描述 原始类型

type Name = string
type Name = number

type 可以描述联合类型

type Easing = "ease-in" | "ease-out" | "ease-in-out";

type 可以描述元祖

// 描述元祖
type Easing = [number, string]

都可以描述数组

interface stringArray {
    [index: number]: string
}
type StringArray = {
    [index: number]: string
}
const myArray: StringArray = ['hello', 'world']

都可以描述对象

interface LabeledValue {
  label: string;
}
type LabeledValue = {
  label: string;
}
const obj: LabeledValue = {
    label: 'nike',
}

描述类

interface ClockInterface {
  currentTime: Date;
  setTime(d: Date): void;
}
class clock implements ClockInterface {
    currentTime: Date = new Date()
    setTime(d: Date) {
        this.currentTime = d
    }
    constructor(h: number, m: number) { 
    }
}

都可以描述函数

interface SearchFunc {
  (source: string, subString: string): boolean;
}
let mySearch: SearchFunc;
mySearch = function (src: string, sub: string): boolean {
  let result = src.search(sub);
  return result > -1;
};
mySearch = function (src, sub) {
  let result = src.search(sub);
  return result > -1;
};
// use type alias
type SetPoint = (x: number, y: number) => void;
let foo: SetPoint
foo = (x, y) => {}

interface 可以 extends

interface Parent { x: number; }
interface Child extends Parent { y: number }
type Parent = { x: number; }
type Child = Parent & { y: number }
type Parent = { x: number; }
interface Child extends Parent { y: number }
interface Parent { x: number; }
type Child = Parent & { y: number }

interface 可以被 implements

类可以以完全相同的方式实现接口或类型别名。

不能实现联合类型的类型别名

interface Point {
  x: number;
  y: number;
}
type Point2 = {
  x: number;
  y: number;
}
class SomePoint implements Point {
  x = 1;
  y = 2;
}
class SomePoint2 implements Point2 {
  x = 1;
  y = 2;
}

interface 可以被 declaration merging

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