title: Typescript

#+startup: content

basic

function greeter(person: string) {
    return "Hello, " + person
}
let user = "Yee"
console.log(greeter(user))

Hello, Yee

function greeter(person: string) {
    return "Hello, " + person
}
"use strict";
let user = [2, 39]
console.log(greeter(user))

../../../../tmp/babel-cIibwh/ts-src-IRbM7W.ts(6,21): error TS2345: Argument of type 'number[]' is not assignable to parameter of type 'string'.
Hello, 2,39

class User{
    Fristname:string
    Lastname:string
    Fullname:string

    constructor(firstname:string, lastname:string){
        this.Fristname = firstname
        this.Lastname = lastname
        this.Fullname = this.Fristname+this.Lastname
    }
}
interface Person{
    Fristname:string
    Lastname:string
}

function Greeter(Person){
    return "hello, "+Person.Fristname + Person.Lastname
}
var user = new User("li", "san")

console.log(Greeter(user))

../../../../tmp/babel-cIibwh/ts-src-DPsbOA.ts(17,18): error TS7006: Parameter 'Person' implicitly has an 'any' type.
hello, lisan

callback

const n: number = 10
let qual = n => n*n;  
let m = (() => {
    console.log('nidh', n, qual(4))
    return 9
})()
console.log(m)

../../../../tmp/babel-KUfP9t/ts-src-HiNQhf.ts(2,12): error TS7006: Parameter 'n' implicitly has an 'any' type.
nidh 10 16
9

let jj = (
    (msg , didi) => {
        console.log(msg);
        didi(msg);
        return 9
    }
)
( "kdiikkjkjk",
  msg => {
      console.log(msg);
  }
)

console.log(jj)

../../../../tmp/babel-KUfP9t/ts-src-SG7pDT.ts(11,3): error TS7006: Parameter 'msg' implicitly has an 'any' type.
kdiikkjkjk
kdiikkjkjk
9

Generic

withour generic

function createArray(value: any, count: number): any[] {
  const arr: any[] = []
  for (let index = 0; index < count; index++) {
    arr.push(value)
  }
  return arr
}

const arr1 = createArray(11, 3)
const arr2 = createArray('aa', 3)
console.log(arr1)
console.log(arr2)
console.log(arr1[0].toFixed(), arr2[0].split(''))

[ 11, 11, 11 ]
[ 'aa', 'aa', 'aa' ]
11 [ 'a', 'a' ]

with generic

function createArray2 <T> (value: T, count: number):T[] {
  const arr: Array<T> = []
  for (let index = 0; index < count; index++) {
    arr.push(value)
  }
  return arr
}
const arr3 = createArray2<number>(11, 3)
console.log(arr3[0].toFixed())
// console.log(arr3[0].split('')) // error
const arr4 = createArray2<string>('aa', 3)
console.log(arr4[0].split(''))
// console.log(arr4[0].toFixed()) // error

11
[ 'a', 'a' ]

advanced example

interface IbaseCRUD <T> {
  data: T[]
  add: (t: T) => void
  getById: (id: number) => T

}

class User {
  id?: number; //id主键自增
  name: string; //姓名
  age: number; //年龄

  constructor (name, age) {
    this.name = name
    this.age = age
  }
}

class UserCRUD implements IbaseCRUD <User> {
  data: User[] = []

  add(user: User): void {
    user = {...user, id: Date.now()}
    this.data.push(user)
    console.log('保存user', user.id)
  }

  getById(id: number): User {
    return this.data.find(item => item.id===id)
  }
}


const userCRUD = new UserCRUD()
userCRUD.add(new User('tom', 12))
userCRUD.add(new User('tom2', 13))
console.log(userCRUD.data)

../../../../tmp/babel-VDC0rp/ts-src-ub8Ktp.ts(13,16): error TS7006: Parameter 'name' implicitly has an 'any' type.
../../../../tmp/babel-VDC0rp/ts-src-ub8Ktp.ts(13,22): error TS7006: Parameter 'age' implicitly has an 'any' type.
保存user 1629717666420
保存user 1629717666424
[
  { name: 'tom', age: 12, id: 1629717666420 },
  { name: 'tom2', age: 13, id: 1629717666424 }
]

interface

class User{
    Fristname:string
    Lastname:string
    Fullname:string

    constructor(firstname:string, lastname:string){
        this.Fristname = firstname
        this.Lastname = lastname
        this.Fullname = this.Fristname+this.Lastname
    }
}
interface Person{
    Fristname:string
    Lastname:string
}

function Greeter(Person){
    return "hello, "+Person.Fristname + Person.Lastname
}
var user = new User("li", "san")

console.log(Greeter(user))

../../../../tmp/babel-VDC0rp/ts-src-kkk0v4.ts(17,18): error TS7006: Parameter 'Person' implicitly has an 'any' type.
hello, lisan

collection

var nn = 10.00002
console.log(+nn.toFixed(2))

my collection