lambda.js

'use strict';

import AWS                                       from "aws-sdk";
import { UserHeaderType }                        from "../../models/types";
import DynamoDB                                  from "../../classes/dynamoDB";
import logger                                    from "../../config/logger";

const handler = async (event: HeaderRequestInterface<UserHeaderType>) => {
  const genaralErrorMessage = "there was an error while checkig business name";
  
  try {
    logger("info", event, "event");
    const missingBusinessErrorMessasge = "there is no business coresponding with the user while getting name of business";
    const noUserInHeaderErrorMessage = "there is no user in header while getting name of business";
    const { ['X-user']: user } = getHeaders<UserHeaderType>(event.headers, noUserInHeaderErrorMessage, "X-user");

    const params: AWS.DynamoDB.DocumentClient.GetItemInput = {
      TableName: process.env.BUSINESS_TABLE,
      Key: {
        email: user
      }
    }
    const business = await DynamoDB.getItem(params, missingBusinessErrorMessasge);
    logger("info", business, "name of business");
    return business;

  } catch(error) {
    logger('error', error);

    const response = error.customErrorMessage ? CustomError.createCustomErrorResponse(400, error.customErrorMessage) : CustomError.createCustomErrorResponse(400, genaralErrorMessage);
    logger("error", response, "errorResponse");
    return response;
  }
}

# to better show what I'm sending 
class CustomError extends Error {
    static createCustomErrorResponse(statusCode: number, errorMessage: string): ResponseType {
        return {
            statusCode,
            body: JSON.stringify({errorMessage}),
        }
    }
    static createCustomErrorMessage(customErrorMessage: string): CustomErrorMessageType {
        return {
            customErrorMessage
        }
    }
}



export { handler };