update-one.ts

import * as AWS from 'aws-sdk';

const TABLE_NAME = process.env.STORE_TABLE_NAME || '';
const PRIMARY_KEY = process.env.STORE_PRIMARY_KEY || '';

const RESERVED_RESPONSE = `Error: You're using AWS reserved keywords as attributes`,
  DYNAMODB_EXECUTION_ERROR = `Error: Execution update, caused a Dynamodb error, please take a look at your CloudWatch Logs.`;

const db = new AWS.DynamoDB.DocumentClient();

export const handler = async (event: any = {}): Promise<any> => {
  if (!event.body) {
    return {
      statusCode: 400,
      body: 'invalid request, you are missing the parameter body',
    };
  }

  const editedItemId = event.pathParameters.id;
  if (!editedItemId) {
    return {
      statusCode: 400,
      body: 'invalid request, you are missing the path parameter id',
    };
  }

  const editedItem: any =
    typeof event.body == 'object' ? event.body : JSON.parse(event.body);
  const editedItemProperties = Object.keys(editedItem);
  if (!editedItem || editedItemProperties.length < 1) {
    return { statusCode: 400, body: 'invalid request, no arguments provided' };
  }

  const firstProperty = editedItemProperties.splice(0, 1);
  const params: any = {
    TableName: TABLE_NAME,
    Key: {
      [PRIMARY_KEY]: editedItemId,
    },
    UpdateExpression: `set ${firstProperty} = :${firstProperty}`,
    ExpressionAttributeValues: {},
    ReturnValues: 'UPDATED_NEW',
  };
  params.ExpressionAttributeValues[`:${firstProperty}`] =
    editedItem[`${firstProperty}`];

  editedItemProperties.forEach((property) => {
    params.UpdateExpression += `, ${property} = :${property}`;
    params.ExpressionAttributeValues[`:${property}`] = editedItem[property];
  });

  try {
    await db.update(params).promise();
    return {
      statusCode: 204,
      headers: {
        'Access-Control-Allow-Origin': '*',
      },
      body: '',
    };
  } catch (dbError: any) {
    const errorResponse =
      dbError.code === 'ValidationException' &&
      dbError.message.includes('reserved keyword')
        ? DYNAMODB_EXECUTION_ERROR
        : RESERVED_RESPONSE;
    return { statusCode: 500, body: errorResponse };
  }
};