8. TypeScript - In Node.js

• Superset of JavaScript, adds static typing, interfaces, generics, etc.

• Compiles down to plain JavaScript.

INSTALLATIONS

npm init -y
npm install typescript ts-node @types/node --save-dev
npx tsc --init
//ts-node: run .ts files directly.
//@types/node: type definitions for Node.js core modules.

Change Some settings in ts.config

"outDir": "./dist",
 "lib": ["esnext"],                
 "types": ["node"],

Changes in package.json

  "scripts": {
     "build":"tsc",  //convert ts into js 
     "start":"node dist/index.js", // In the dist folder our index.js file run 
     "dev":"ts-node index.ts"  // run our ts file
  },

npm run build // convert ts to plain js in dist
npm run dev // run ts file
npm start // run js file inside dist ts and js file both give same result

BASIC TYPES

//Basic types
let isDone:Boolean = false;
let name:String = "Ayush";
let num: number = 23;

let list:number[] = [1,2,3,4,5] // Array<number> also works
let randomVal: any ="hey" // type is any - string number boolean 

let abc :[string , number] = ["hi",66] //tuple

enum Color{
    Blue , Green , Red
}
let d:Color = Color.Blue

Interfaces

Interface define the structure/shape of the object or data. Let suppose we have User having name , id ,email . So we need to verify its types before creating User.

// Interface
interface User{
    name: String;
    id:number;
    email?:string;
    readonly createdAt: Date;
}

const user : User ={
    name:'Ayush',
    id:1,
    createdAt:new Date(),
}
//type
type Product ={
    title:string,
    price:number
}
const product1 : Product={
    title:"One plus nord 5",
    price:32000,
}

Functions

//functions with type annotations
function add(a:number,b:number):number{
    return a+b;
}
//with arrow function
const mul = (a:number,b:number):number=> {
    return a*b;
}

function greet(a:string , greeting?:string){ // here greeting is optional to pass
    return `${a} + ${greeting}`
}

TypeScript With Node.js and Express.js Integration

npm install express nodemon
npm install @types/express --save-dev

 "scripts": {
    "build": "tsc",
    "start": "node dist/index.js",
    "dev": "nodemon index.ts"
  },

import express ,{Express , NextFunction, Request , Response} from 'express';

const app:Express = express();
const port:number = 3000;

app.use(express.json())

interface CustomRequest extends Request{
    startTime?:number
}
//use middleware
app.use((req:CustomRequest , res:Response , next: NextFunction)=>{
    req.startTime = Date.now();
    next();
})

// req -> Request<p->like dynimic value /:id, ResBody-> res body like res.json , res.send , ReqBody-> need to create interface destrcutres data types , ReqQuery, Locals>
app.get('/' , (req:Request,res:Response)=>{
    res.send("Hello Express js with typeScript")
})
//post route -> new user : name , email - req.body
// /user/:id?name -> Request<{},{},{},{}>
interface User{
    name:string,
    email:string
}
app.post('/user', (req:Request<{}, {}, User> ,res:Response)=>{
    const{name , email}= req.body;
    res.status(200).json({
        sucess:true,
        message:"User creted"
    })
})
//user bases id
app.get('/user/:id', (req:Request<{id:String}> ,res:Response)=>{
    const{id} = req.params;
    res.json({
        userId:id
    })
})

app.listen(port , ()=>{
    console.log(`Server is running at ${port}`)
})

Mongoose models using Typscript

npm i mongoose
npm i @types/mongoose --save-dev

import mongoose, { Document, Schema } from 'mongoose'

export interface IUser extends Document { // we export this cuz we use this in our controller 
  name: string;                           // const users : IUser[]= await User.find(...)
  email: string;
  password: string;
  createdAt: Date;
}

const userSchema = new Schema<IUser>({
  name: { type: String, required: true },
  email: { type: String, required: true },
  password: { type: String, required: true },
  createdAt: Date
});

export default mongoose.model<IUser>("User", userSchema);