AWS SDK for JavaScript/Node.js in DynamoDB

Introduction

The AWS SDK for JavaScript/Node.js helps you talk to AWS services like DynamoDB easily from your JavaScript code.

You want to save or read data from a DynamoDB database in your Node.js app.

You need to automate AWS tasks like uploading files to S3 or sending messages with SNS.

You want to build a web app that interacts with AWS services without manual setup.

You want to write scripts that manage AWS resources programmatically.

You want to connect your backend code to AWS services securely and efficiently.

Syntax

DynamoDB

import { DynamoDBClient, PutItemCommand } from "@aws-sdk/client-dynamodb";

const client = new DynamoDBClient({ region: "us-east-1" });

const command = new PutItemCommand({
  TableName: "YourTableName",
  Item: {
    "PrimaryKey": { S: "keyValue" },
    "Attribute": { S: "value" }
  }
});

async function run() {
  const response = await client.send(command);
  console.log(response);
}

run();

Use import to bring in AWS SDK modules.

Create a client for the AWS service you want to use, like DynamoDBClient.

Examples

This example reads an item with UserId '123' from the 'Users' table.

DynamoDB

import { DynamoDBClient, GetItemCommand } from "@aws-sdk/client-dynamodb";

const client = new DynamoDBClient({ region: "us-west-2" });

const command = new GetItemCommand({
  TableName: "Users",
  Key: {
    "UserId": { S: "123" }
  }
});

async function run() {
  const response = await client.send(command);
  console.log(response.Item);
}

run();

This example deletes an item with OrderId 'order123' from the 'Orders' table.

DynamoDB

import { DynamoDBClient, DeleteItemCommand } from "@aws-sdk/client-dynamodb";

const client = new DynamoDBClient({ region: "eu-central-1" });

const command = new DeleteItemCommand({
  TableName: "Orders",
  Key: {
    "OrderId": { S: "order123" }
  }
});

async function run() {
  await client.send(command);
  console.log('Item deleted successfully');
}

run();

Sample Program

This program adds an item with Id '001' and Name 'Alice' to the DynamoDB table named 'TestTable'. It prints success or error messages.

DynamoDB

import { DynamoDBClient, PutItemCommand } from "@aws-sdk/client-dynamodb";

async function addItem() {
  const client = new DynamoDBClient({ region: "us-east-1" });

  const command = new PutItemCommand({
    TableName: "TestTable",
    Item: {
      "Id": { S: "001" },
      "Name": { S: "Alice" }
    }
  });

  try {
    const response = await client.send(command);
    console.log("Item added successfully", response);
  } catch (error) {
    console.error("Error adding item", error);
  }
}

addItem();

Important Notes

Always specify the AWS region when creating the client.

Use async/await to handle asynchronous calls cleanly.

Catch errors to handle failures gracefully.

Summary

The AWS SDK for JavaScript/Node.js lets you work with AWS services in your code.

Create a client, build a command, and send it to perform actions.

Use async/await and error handling for smooth operation.

Practice

1. What is the first step to interact with DynamoDB using the AWS SDK for JavaScript/Node.js?

easy

A. Create a DynamoDB client instance

B. Write a SQL query

C. Install a database driver

D. Open a database connection manually

Solution

1. Step 1: Understand AWS SDK usage

   To work with DynamoDB, you first create a client object that represents the service.

2. Step 2: Recognize the role of the client

   The client handles requests and responses to DynamoDB; no manual connection or SQL is needed.

3. Final Answer:

   Create a DynamoDB client instance -> Option A

4. Quick Check:

   Client creation = First step [OK]

Hint: Always start by creating the service client [OK]

Common Mistakes:

• Trying to write SQL queries for DynamoDB
• Assuming manual connection is needed
• Skipping client creation

2. Which of the following is the correct way to import the DynamoDB client from AWS SDK v3 in Node.js?

easy

A. const DynamoDBClient = require('@aws-sdk/client-dynamodb');

B. const { DynamoDBClient } = require('aws-sdk');

C. import { DynamoDBClient } from '@aws-sdk/client-dynamodb';

D. import DynamoDBClient from 'aws-sdk';

Solution

1. Step 1: Identify AWS SDK v3 import style

   AWS SDK v3 uses ES modules and named imports from '@aws-sdk/client-dynamodb'.

2. Step 2: Match correct syntax

   import { DynamoDBClient } from '@aws-sdk/client-dynamodb'; uses ES module import with correct package and named import syntax.

3. Final Answer:

   import { DynamoDBClient } from '@aws-sdk/client-dynamodb'; -> Option C

4. Quick Check:

   ES module named import = import { DynamoDBClient } from '@aws-sdk/client-dynamodb'; [OK]

Hint: Use ES module imports from '@aws-sdk/client-dynamodb' [OK]

Common Mistakes:

• Using old AWS SDK v2 import style
• Using default import instead of named import
• Mixing require and import syntax

3. Given the following code snippet, what will be logged if the item exists in the DynamoDB table?

import { DynamoDBClient, GetItemCommand } from '@aws-sdk/client-dynamodb';
const client = new DynamoDBClient({ region: 'us-east-1' });

async function getItem() {
  const command = new GetItemCommand({
    TableName: 'Users',
    Key: { 'UserId': { S: '123' } }
  });
  const response = await client.send(command);
  console.log(response.Item);
}
getItem();

medium

A. Undefined because no item exists

B. An empty object {}

C. An error is thrown due to missing parameters

D. The item object with attributes if found

Solution

1. Step 1: Understand GetItemCommand behavior

   GetItemCommand returns an object with an Item property if the item exists.

2. Step 2: Analyze console.log output

   Logging response.Item will show the item's attributes as an object if found.

3. Final Answer:

   The item object with attributes if found -> Option D

4. Quick Check:

   response.Item = item object [OK]

Hint: GetItemCommand returns Item if found, else undefined [OK]

Common Mistakes:

• Expecting an error when item is missing
• Assuming response itself is the item
• Confusing empty object with undefined

4. What is wrong with the following code snippet that tries to put an item into DynamoDB?

import { DynamoDBClient, PutItemCommand } from '@aws-sdk/client-dynamodb';
const client = new DynamoDBClient({ region: 'us-east-1' });

async function putItem() {
  const command = new PutItemCommand({
    TableName: 'Users',
    Item: { UserId: '123', Name: 'Alice' }
  });
  await client.send(command);
}
putItem();

medium

A. TableName should be lowercase

B. Item attributes must be wrapped with DynamoDB data types like { S: 'value' }

C. PutItemCommand does not exist in AWS SDK

D. Missing await before client.send

Solution

1. Step 1: Check Item attribute format

   DynamoDB expects attribute values wrapped in type descriptors like { S: 'string' }.

2. Step 2: Identify the error cause

   Passing plain strings without type wrappers causes validation errors.

3. Final Answer:

   Item attributes must be wrapped with DynamoDB data types like { S: 'value' } -> Option B

4. Quick Check:

   Attribute values need type wrappers [OK]

Hint: Always wrap attribute values with DynamoDB types (S, N, etc.) [OK]

Common Mistakes:

• Passing plain strings instead of typed attributes
• Assuming table names are case-insensitive
• Forgetting to await async calls

5. You want to update a user's email in DynamoDB using AWS SDK for JavaScript/Node.js. Which approach correctly updates only the email attribute without overwriting the entire item?

const command = new UpdateItemCommand({
  TableName: 'Users',
  Key: { UserId: { S: '123' } },
  UpdateExpression: 'SET Email = :email',
  ExpressionAttributeValues: { ':email': { S: '[e-mail]' } }
});
await client.send(command);

hard

A. This code correctly updates only the Email attribute

B. UpdateExpression should be 'ADD Email :email' to update

C. You must use PutItemCommand to update attributes

D. ExpressionAttributeValues keys should not start with ':'

Solution

1. Step 1: Understand UpdateItemCommand usage

   UpdateExpression with 'SET' updates specified attributes without replacing the whole item.

2. Step 2: Verify ExpressionAttributeValues syntax

   Keys start with ':' and values use DynamoDB types, matching the expression.

3. Step 3: Confirm no overwrite occurs

   Using UpdateItemCommand with SET updates only Email, preserving other attributes.

4. Final Answer:

   This code correctly updates only the Email attribute -> Option A

5. Quick Check:

   UpdateExpression SET = partial update [OK]

Hint: Use UpdateItemCommand with SET to update attributes safely [OK]

Common Mistakes:

• Using PutItemCommand which overwrites entire item
• Using ADD instead of SET for attribute update
• Removing ':' prefix in ExpressionAttributeValues keys