function calculateSum(a, b) {
  if (typeof a === 'number' && typeof b === 'number') {
  	const result = a + b;
    return result;
  } else {
  	throw new Error('Invalid arguments');
  }
}

class DataProcessor {
  constructor(data) {
    this.data = data;
  	this.processed = false;
  }

  processData() {
    if (!this.data) {
    	return null;
    }

    const results = this.data.map(item => {
    	return {
      	original: item,
        transformed: this.transform(item)
      };
    });

  	this.processed = true;
    return results;
  }

  transform(item) {
    return item.toUpperCase();
  }
}

const processor = new DataProcessor(['hello', 'world']);
const results = processor.processData();

console.log('Results:', results);

async function fetchUserData(userId) {
  try {
  	const response = await fetch(`/api/users/${userId}`);
    const data = await response.json();
  	return data;
  } catch (error) {
  	console.error('Error:', error);
    return null;
  }
}

export { calculateSum, DataProcessor, fetchUserData };