An example of working with dynamodb from nodejs.

DynamoDbManager.js

/**
 * Helper class that interacts with DynamoDB to read and write data.
 */
class DynamoDbManager {

  constructor() {
    const AWS = require("aws-sdk")

    AWS.config.update({
      region: "us-east-2",
      endpoint: "dynamodb.us-east-2.amazonaws.com"
    })

    this.docClient = new AWS.DynamoDB.DocumentClient()
  }

  /**
   * Pulls data from DynamoDB for previous levels' stats for the current session.
   *
   * @param {string} sessionId
   * @returns {Promise<any>}
   */
  getDynamoScoresForSession(sessionId) {
    return new Promise((resolve, reject) => {

      const params = {
        TableName: process.env.DynamoScoresTable,
        KeyConditionExpression: 'sessionId= :sessionId',
        ExpressionAttributeValues: {
          ':sessionId': sessionId
        }
      }

      this.docClient.query(params, function (err, data) {
        if (err) reject(err)
        else resolve(data)
      })
    })
  }

  /**
   * Pulls data from DynamoDB for the number of levels in a specified session.
   *
   * @param {string} sessionId
   * @returns {Promise<any>}
   */
  getLevelsForSession(sessionId) {
    return new Promise((resolve, reject) => {

      const params = {
        TableName: process.env.DynamoLevelsTable,
        KeyConditionExpression: 'sessionId= :sessionId',
        ExpressionAttributeValues: {
          ':sessionId': sessionId
        }
      }

      this.docClient.query(params, function (err, data) {
        if (err) reject(err)
        else resolve(data)
      })
    })
  }

  /**
   * Takes a DynamoDB table name and a item. Uses the DynamoDB "put" operation to save the item to the table.
   *
   * @param {string} table
   * @param {} item
   * @returns {Promise<any>}
   */
  writeData(table, item) {
    return new Promise((resolve, reject) => {

      const params = {
        ReturnValues: 'NONE',
        TableName: table,
        Item: item
      }

      this.docClient.put(params, (err, data) => {
        if (err) reject(err)
        else resolve(data)
      })
    })
  }


  saveLevelScore() {
    return new Promise((resolve, reject) => {
      resolve('chyeah')
    })
  }

  /**
   * Deletes all data in the DynamoLevelsTable and SessionLevels table for a given sessionId.
   *
   * @param previousLevelsSessionData
   * @param lastLevelData
   * @returns {Promise<any>}
   */
  deleteAllDynamoSessionData(previousLevelsSessionData, lastLevelData) {
    return new Promise((resolve, reject) => {

      const scoresRankingsToDelete = []

      previousLevelsSessionData.forEach(previousLevelData => {
        scoresRankingsToDelete.push({
          DeleteRequest: {
            Key: {
              'sessionId': previousLevelData.sessionId,
              'levelId': previousLevelData.levelId
            }
          }
        })
      })

      scoresRankingsToDelete.push({
        DeleteRequest: {
          Key: {
            'sessionId': lastLevelData.session,
            'levelId': lastLevelData.levelId
          }
        }
      })

      const sessionLevelsToDelete = [{
        DeleteRequest: {
          Key: {
            'sessionId': lastLevelData.session
          }
        }
      }]

      const params = {
        RequestItems: {
          [process.env.DynamoScoresTable]: scoresRankingsToDelete,
          [process.env.DynamoLevelsTable]: sessionLevelsToDelete
        }
      }

      this.docClient.batchWrite(params, function (err, data) {
        if (err) reject(err)
        else resolve(data)
      })
    })
  }

}

module.exports = new DynamoDbManager()