Error Handling

{
  "errorCode": "USER.0001",
  "message": ["User not found"],
  "statusCode": "404",
  "arguments": [
    {
      "key": "userId",
      "value": "invalid-id"
    }
  ]
}

class KillBAPIError extends Error {
  constructor(response) {
    super(response.message.join(', '));
    this.errorCode = response.errorCode;
    this.statusCode = response.statusCode;
    this.arguments = response.arguments;
  }
}

const makeAPIRequest = async (endpoint, options) => {
  try {
    const response = await fetch(endpoint, options);
    
    if (!response.ok) {
      const error = await response.json();
      throw new KillBAPIError(error);
    }
    
    return await response.json();
    
  } catch (error) {
    if (error instanceof KillBAPIError) {
      // Handle API errors
      console.error(`API Error ${error.errorCode}:`, error.message);
      
      if (error.statusCode === '401') {
        // Token expired, refresh
        await refreshToken();
        return makeAPIRequest(endpoint, options);
      }
      
      if (error.errorCode === 'RAMP.0001') {
        // Quotation expired, get new one
        const newQuote = await getNewQuotation();
        // Retry with new quote
      }
    }
    
    throw error;
  }
};

const retryWithBackoff = async (fn, maxRetries = 3) => {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await fn();
    } catch (error) {
      if (i === maxRetries - 1) throw error;
      
      // Don't retry client errors (4xx)
      if (error.statusCode && error.statusCode < 500) {
        throw error;
      }
      
      // Exponential backoff
      const delay = Math.pow(2, i) * 1000;
      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }
};

// Usage
const user = await retryWithBackoff(() => createUser(userData));

const getUserMessage = (error) => {
  const messages = {
    'AUTH.0002': 'Your session expired. Please log in again.',
    'USER.0003': 'This email is already registered.',
    'RAMP.0001': 'The price quote expired. Please try again.',
    'RAMP.0003': 'Transaction amount exceeds your limit. Please verify your identity to increase limits.'
  };
  
  return messages[error.errorCode] || 'An error occurred. Please try again.';
};