Nest JS Documentation 1

Installation Nest JS

$ npm i -g @nestjs/cli
$ nest new project-name

Alternatives Way To Install Nest JS

$ git clone https://github.com/nestjs/typescript-starter.git project
$ cd project
$ npm install
$ npm run start

Decorators In NestJS

┌───────────────────────┬──────────────────┬──────────────────────────────┐
│ Type                  │ Example          │ Use Case                      │
├───────────────────────┼──────────────────┼──────────────────────────────┤
│ Class Decorators      │ @Controller()    │ Defines controllers & modules │
│ Method Decorators     │ @Get(), @Post()  │ Handles HTTP requests         │
│ Property Decorators   │ @Inject()        │ Injects dependencies          │
│ Parameter Decorators  │ @Param(), @Body()│ Extracts request data         │
│ Custom Decorators     │ @Log()           │ Adds reusable logic           │
└───────────────────────┴──────────────────┴──────────────────────────────┘

constrollers
controllers can handel the incoming requests
and sending to the response to the clint

Example for to create simple API using Controller and Get Decorator

import {Controller, Get} from '@nestjs/common';

@Controller('all-students')
export class allStudents(){
 @Get()
 findAllStudents():string{
  return "This is All Students Response"
 }
}

Providers In NestJs
In NestJs Provider is a class that can be Injected into other classes using Dependency Injection (ID)

Example user.service.ts

import {Injectable} from '@nestjs/common';

@Injectable()
export class UserService{
 private users=[
  {id:1,name:"Aishwary"},
  {id:2,name:"Harsh"},
  {id:3,name:"Ambuj"},
  {id:4,name:"Somyadeb"},
  {id:5,name:"Shubham"},
  {id:6,name:"Anish"}
 ];

 getUserById(id:number){
  return this.user.find(user=>user.id===id);
 }
}

Example user.controller.ts

import {Controller,Get,Param} from '@nestjs/common';
import {UserService} from './user.service';

export class UserController{
 constructor(private readonly userService:UserServivce){}

 @Get('user')
 getUser(@Param(':id')id:string){
  return this.userService.getUserById(Number(id));
 }
}

Example user.module.ts

import {module} from '@nestjs/common';
import {UserSerive} from './user.service';
import {UserController} from './uer.controller';

@Module({
 controllers:[UserController],
 providers:[Userservice],
)}
export class UserModule {}

Example app.module.ts

import {Module} from '@nestjs/common';
import {UserModule} from  './user/user.module';

@Module({
 import:[UserModule],
})
export class AppModuel{}