Next.js API Route Handler with error handling

api-error.ts

/**
 * Represents an error that occurs when data fails to validate against the API's expected schema or requirements.
 * This class extends the native JavaScript `Error` class, adding a `statusCode` property to facilitate API error handling.
 *
 * @example
 * // Throws an APIValidationError with a custom message and a 400 Bad Request status code.
 * throw new APIValidationError('Invalid user input', 400);
 *
 * @extends Error
 */
export class APIValidationError extends Error {
  /**
   * The HTTP status code that should be returned to the client when this error occurs.
   *
   * @type {number}
   */
  statusCode: number

  /**
   * Creates an instance of APIValidationError.
   *
   * @param {string} message - The error message that describes the validation failure.
   * @param {number} statusCode - The HTTP status code associated with this kind of validation error.
   * Commonly used codes include 400 for Bad Request or 422 for Unprocessable Entity.
   */
  constructor(message: string, statusCode: number) {
    super(message)
    this.name = 'ValidationError'
    this.statusCode = statusCode
  }
}

route.ts

import { APIValidationError } from './api-error'

// GET /api/blog/1234-whatever
export async function GET(
  request: Request,
  { params }: { params: { id: string } }
) {
  try {
    if (params.id) {
        return Response.json(
          { status: 'success', message: 'Vote Recorded' },
          { status: 200 }
        )
    } else {
      throw new APIValidationError('Invalid blogpost [id]', 410)
    }
  } catch (error) {
    if (error instanceof APIValidationError) {
      return Response.json(
        { status: 'error', message: error.message },
        { status: error.statusCode }
      )
    } else {
      return Response.json(
        { status: 'error', message: 'Unknown error occurred' },
        { status: 500 }
      )
    }
  }
}