📝 Introduction to NestJS with CRUD Example

🌟 What is NestJS?

NestJS is a progressive Node.js framework built with TypeScript. It helps developers build scalable and maintainable backend applications by providing structure and features like:

• Modules → Group related features (like PropertyModule).

• Controllers → Handle incoming requests and send responses.

• Services → Contain business logic (optional in small demos).

• Decorators → Special keywords like @Controller, @Get, @Post to define routes.

Think of NestJS as a structured version of ExpressJS. If ExpressJS is minimal and flexible, NestJS is organized and opinionated, making it great for larger projects.

⚙️ Setup

1. Install NestJS CLI globally:

   npm i -g @nestjs/cli
   

2. Create a new project:

   nest new property-api
   

3. Move into the project folder:

   cd property-api
   

4. Run the server in development mode:

   npm run start:dev
   

📂 Folder Structure

When you generate a new module and controller for property, NestJS organizes code like this:

src/
│── main.ts
│── app.module.ts
│
└── property/
    │── property.module.ts
    │── property.controller.ts

📝 Complete CRUD Example

src/main.ts

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  await app.listen(3000);
  console.log('🚀 Server running on http://localhost:3000');
}
bootstrap();

src/app.module.ts

import { Module } from '@nestjs/common';
import { PropertyModule } from './property/property.module';

@Module({
  imports: [PropertyModule],
})
export class AppModule {}

src/property/property.module.ts

import { Module } from '@nestjs/common';
import { PropertyController } from './property.controller';

@Module({
  controllers: [PropertyController],
})
export class PropertyModule {}

src/property/property.controller.ts

import { Controller, Get, Post, Put, Delete, Param, Body } from '@nestjs/common';

let properties = [
  { id: 1, name: 'Property One', type: 'Condo' },
  { id: 2, name: 'Property Two', type: 'House' }
];

@Controller('property')
export class PropertyController {
  // GET all
  @Get()
  findAll() {
    return properties;
  }

  // GET one
  @Get(':id')
  findOne(@Param('id') id: string) {
    return properties.find(p => p.id == id) || { message: 'Not found' };
  }

  // POST create
  @Post()
  create(@Body() body: any) {
    const newProperty = { id: properties.length + 1, ...body };
    properties.push(newProperty);
    return newProperty;
  }

  // PUT update
  @Put(':id')
  update(@Param('id') id: string, @Body() body: any) {
    const property = properties.find(p => p.id == id);
    if (!property) return { message: 'Not found' };
    Object.assign(property, body);
    return property;
  }

  // DELETE
  @Delete(':id')
  remove(@Param('id') id: string) {
    properties = properties.filter(p => p.id != id);
    return { message: `Property ${id} deleted` };
  }
}

🚀 How to Test

• GET → http://localhost:3000/property → Returns all properties

• GET → http://localhost:3000/property/1 → Returns one property

• POST → http://localhost:3000/property → Adds new property

• PUT → http://localhost:3000/property/1 → Updates property

• DELETE → http://localhost:3000/property/1 → Deletes property

✅ With this simple CRUD example, you’ve learned:

• How NestJS apps are structured

• How to use @Controller, @Get, @Post, @Put, @Delete

• How to handle routes, parameters, and body data

👉 Next step: Compare this with ExpressJS CRUD example to see the difference in style and complexity.

Would you like me to add the ExpressJS CRUD example immediately after this NestJS section (so readers can directly compare)?

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