TypeScript基础知识

命令

• 查看版本：tsc -v
• 运行ts文件：tsc xx.ts

数据类型

// basic types
let isDone: boolean = false
let age: number = 10

let firstName: string = 'viking'
let message: string = `Hello, ${firstName}`

let u: undefined = undefined
let n: null = null

let num: string = null

let notSure: any = 4
notSure = 'maybe a string'
notSure = true

notSure.myName
notSure.getName()

// array
let arrOfNumbers: number[] = [1, 2, 3, 4]
arrOfNumbers.push(3)


// tuple
let user: [string, number] = ['viking', 20]
user = ['viking', 30]

// function
function add(x: number, y: number, z:number): number {
  return x + y
}
//let result = add(2, 3)
let add2 = (x: number, y:number): number => {
  return x + y
}

接口Interface

interface Person {
  readonly id: number;  // 只读
  name: string;
  age?: number; // 可选类型（可继承可不继承）
}

let viking: Person = {
  name: 'viking',
  age: 20,
  id: 1
}

const sum = (x: number, y: number) => {
  return x + y
}
interface ISum {
  (x: number, y: number): number
}
const sum2: ISum = sum

interface RandomMap { // 可索引类型（对象随意传）
  [propName: string]: string;
}
const test: RandomMap = {
  a: 'hello',
  b: 'test',
  c: 'test'
}
interface LikeArray {
  [index: number]: string
}

const likeArray: LikeArray = ['1', '2', '3']

// duck typing

interface FunctionWithProps {
  (x: number): number;
  name: string;
}
const a: FunctionWithProps = (x: number) => {
  return x
}
a.name = 'abc'

类和接口

泛型基础知识

function echo<T>(arg: T): T { // 泛型，可识别可调用的方法。例如是整型，可调用整形下的方法
  return arg
}

function swap<T, U>(tuple: [T, U]): [U, T] {  // 返回调换位置
  return [tuple[1], tuple[0]]
}
const result = swap(['string', 123])
let test = 123

interface GithubResp {
  name: string;
  count: number;
}
interface CountryResp {
  name: string;
  area: number;
  population: number;
}

function withAPI<T>(url: string): Promise<T> {
  return fetch(url).then(resp => resp.json())
}
withAPI<CountryResp>('country.resp').then(resp => {
  
})

定义文件 基础知识

/**
 * 文件名称：myFetch.d.ts
 * 如果以.d.ts后缀的文件是：声明文件
 *
 *

  调用方式：
  myFetch.get<number>('test').then(data => {
    // data是number类型
  })

 *
 */
type HTTPMethod = 'GET' | 'POST' | 'PATCH' | 'DELETE'
// T = any默认值为any，也可以不传
declare function myFetch<T = any>(url: string, method: HTTPMethod, data?: any) : Promise<T>

declare namespace myFetch {
  const get: <T = any>(url: string) => Promise<T>;
  const post: <T = any>(url: string, data: any) => Promise<T>;
}

export = myFetch