TILs - Fueling Curiosity, One Insight at a Time

// Get current date-time
const now = Temporal.Now.plainDateTimeISO();
console.log(now.toLocaleString()); // "6/18/2025, 6:01:52 PM"

// Time zone conversion
const nyMeeting = Temporal.ZonedDateTime.from('2025-06-18T10:00[America/New_York]');
const kolkataTime = nyMeeting.withTimeZone('Asia/Kolkata');
console.log(kolkataTime.toLocaleString()); // "6/18/2025, 7:30:00 PM GMT+5:30"

const start = Temporal.PlainDate.from('2025-01-01');
const end = Temporal.PlainDate.from('2025-06-18');
const diff = start.until(end);
console.log(diff.toLocaleString()); // "168 days"

SELECT "orders".* FROM "orders" WHERE "orders"."order_request_id" = 123;

SELECT "order_requests".* 
FROM "order_requests"
INNER JOIN "orders" ON "orders"."order_request_id" = "order_requests"."id";

SELECT "order_requests".* FROM "order_requests" WHERE ...
SELECT "orders".* FROM "orders" WHERE "order_request_id" IN (1, 2, 3, ...)

// roles.decorator.ts
import { SetMetadata } from '@nestjs/common';

export const Roles = (...roles: string[]) => SetMetadata('roles', roles);

// roles.guard.ts
@Injectable()
export class RolesGuard implements CanActivate {
  constructor(private reflector: Reflector) {}

  canActivate(context: ExecutionContext): boolean {
    const requiredRoles = this.reflector.get<string[]>(
      'roles',
      context.getHandler()
    );

    const request = context.switchToHttp().getRequest();
    const user = request.user;

    return requiredRoles?.includes(user?.role); // Check if user has the role
  }
}

@UseGuards(RolesGuard)
@Roles('Admin')
@Patch(':id')
updateOrg() {
  // This route is accessible only to users with the 'Admin' role
}

npm install --save @nestjs/event-emitter

// app.module.ts
import { EventEmitterModule } from '@nestjs/event-emitter';

@Module({
  imports: [
    EventEmitterModule.forRoot(),
  ],
})
export class AppModule {}

// user.service.ts
import { EventEmitter2 } from '@nestjs/event-emitter';

@Injectable()
export class UserService {
  constructor(private eventEmitter: EventEmitter2) {}

  async createUser(userDto: CreateUserDto) {
    const user = await this.userRepository.save(userDto);
    
    this.eventEmitter.emit('user.created', user); // 🔥

    return user;
  }
}

// user.listener.ts
import { OnEvent } from '@nestjs/event-emitter';

@Injectable()
export class UserListener {
  @OnEvent('user.created')
  handleUserCreatedEvent(payload: any) {
    console.log('User created!', payload);
    // Trigger welcome email, analytics, etc.
  }
}

const mockFn = jest.fn();
mockFn('arg'); 
expect(mockFn).toHaveBeenCalledWith('arg');

const obj = {
  greet: () => 'Hello',
};

const spy = jest.spyOn(obj, 'greet');
obj.greet();
expect(spy).toHaveBeenCalled();

git reflog

git reset --hard <commit-hash>

import { useQuery } from '@tanstack/react-query';
import axios from 'axios';

const fetchOrganisations = async () => {
  const { data } = await axios.get('/api/organisations');
  return data;
};

const Users = () => {
  const { data, isLoading, error } = useQuery(['organisations'], fetchOrganisations);

  if (isLoading) return <p>Loading...</p>;
  if (error) return <p>Error fetching organisations</p>;

  return (
    <ul>
      {data.map(organisation => (
        <li key={organisation.id}>{organisation.name}</li>
      ))}
    </ul>
  );
};

const user = {
  role: 'admin',
} as const;

user.role = 'editor'; // ❌ Error: Cannot assign to 'role' because it is a read-only property.

const products = [
  { name: "T-shirt", category: "clothes", price: 50 },
  { name: "Apple", category: "food", price: 5 },
  { name: "Shoes", category: "clothes", price: 35 },
  { name: "Orange", category: "food", price: 7.5 },
  { name: "Blueberry", category: "food", price: 4.5 }
];

const grouped = Object.groupBy(products, product => product.category);

console.log(grouped);

{
  clothes: [
    { name: "T-shirt", category: "clothes", price: 50 },
    { name: "Shoes", category: "clothes", price: 35 }
  ],
  food: [
    { name: "Apple", category: "food", price: 5 },
    { name: "Orange", category: "food", price: 7.5 },
    { name: "Blueberry", category: "food", price: 4.5 }
  ]
}

.PHONY: run-script

# Target to run a long command
run-script:
\t@echo "Running a long command..."
\tsleep 5  # Simulate a long-running command
\t@echo "Command completed."

make run-script

[] == ![]  
=> [] == false  
=> +[] == +false  
=> 0 == 0  
=> true

// user.service.ts
@Injectable()
export class UserService {
  getUsers() {
    return ['Alice', 'Bob'];
  }
}

// user.module.ts
@Module({
  controllers: [UserController],
  providers: [UserService],
})
export class UserModule {}

// user.controller.ts
@Controller('users')
export class UserController {
  constructor(private readonly userService: UserService) {}

  @Get()
  findAll() {
    return this.userService.getUsers();
  }
}

class Event < ApplicationRecord
  validates_timeliness :start_time, on_or_after: :now, type: :datetime
end

https://localhost:3000/employer/job_posts/2/job_applications/new

https://localhost:3000/employer/job_posts/frontend-developer-37b70ea4-761e-4369-832e-f5b373f7f00b/job_applications/new

rails_representation_url(
  image.variant(resize_to_limit: [300, 300], saver: { quality: 80 }, format: :webp).processed,
  only_path: true
)