Using AWS DynamoDB with JavaScript

The following are examples of using CosmosDB from a Lambda function.

Initialization:

const AWS = require('aws-sdk');

const ddb = new AWS.DynamoDB.DocumentClient({ apiVersion: '2012-08-10', region: process.env.AWS_REGION });
const { CONNECTIONS_TABLE } = process.env;

Create item:

/**
 * @param {string} connectionId
 */
const createConnection = async (connectionId) => {
  await ddb.put({
    TableName: CONNECTIONS_TABLE,
    Item: {
      connectionId: connectionId
    }
  }).promise();
};

Delete item:

/**
 * @param {string} connectionId 
 */
const deleteConnection = async (connectionId) => {
  await ddb.delete({
    TableName: CONNECTIONS_TABLE,
    Key: {
      connectionId: connectionId
    }
  }).promise();
};

Get all items. You generally don't want to use the following scan command for production, because it extremely inefficient and will scan your entire database. You can probably only use it if you 100% sure that your database is going to be very small.

/**
 * @returns {Promise<Array<{connectionId:string}>>}
 */
const getConnectionIds = async () => {
  let scanData = await ddb.scan({
    TableName: CONNECTIONS_TABLE,
    ProjectionExpression: 'connectionId' 
  }).promise();

  return scanData.Items;
};