Which of the following is considered a client-side technology?

JavaScript is recognized as a client-side technology because it is primarily executed in the user's web browser, allowing for dynamic content and interactive user interfaces without the need for constant communication with a server. This capability enables the modification of HTML and CSS in real time, enhancing the user experience by facilitating features such as form validations, animations, and async content loading.

On the other hand, PHP, ASP.NET, and Ruby on Rails are server-side technologies. They process data and perform operations on the server, delivering the results to the client browser. PHP is used for web development and runs on the server to generate HTML, while ASP.NET is a framework for building web applications on Microsoft servers. Ruby on Rails is a web application framework that relies on the Ruby programming language to manage server-side logic. Since these technologies handle tasks on the server, they do not provide the direct interactive features that client-side technologies like JavaScript do.