Which AWS SDK allows developers to build applications in JavaScript?

The AWS SDK for JavaScript is specifically designed for developers who want to build applications using JavaScript. This SDK provides a set of tools that allow developers to interact seamlessly with AWS services directly in their JavaScript applications, whether that's in a Node.js environment on the server side or in web applications running in the browser.

Using this SDK makes it easier to manage AWS resources, integrate with various services like DynamoDB, S3, and Lambda, and perform operations such as uploading files, querying databases, or invoking functions without needing to build custom HTTP requests. The SDK also handles various complexities like authentication, request signing, and response parsing which simplifies the coding process for developers.

In contrast, the other AWS SDKs mentioned are tailored for different programming languages. Each of those SDKs serves the specific language ecosystem they are built for, resulting in SDKs that do not support JavaScript. As a result, for working with JavaScript, the AWS SDK for JavaScript is the only and optimal choice.