JavaScript was originally developed for client-side (front-end) programming, allowing developers to create dynamic and interactive web pages. However, over the years, it has evolved significantly and can now be used for server-side (back-end) programming as well. Here's an overview of that evolution:

JavaScript on the Client-side

In 1995, JavaScript was introduced by Netscape Communications to add interactivity to web pages. At this point, JavaScript was purely a client-side language, meaning it ran in the user's browser and was used to make web pages interactive, responsive, and dynamic. For instance, it could be used to validate form inputs, animate page elements, handle user events like clicks or key presses, and more.

Node.js and JavaScript on the Server-side

In 2009, Ryan Dahl introduced Node.js, a runtime environment that allowed JavaScript to be used outside of the browser, particularly on the server-side. Node.js uses the V8 JavaScript engine (originally developed by Google for Chrome) to execute JavaScript code on a server.

With Node.js, developers could now use JavaScript to handle HTTP requests and responses, access databases, manage file systems, and much more. This meant that JavaScript could now be used to build the entire web application, both client-side and server-side, making it a full-stack language. This is often referred to as JavaScript's "MEAN" (MongoDB, Express.js, AngularJS, Node.js) or "MERN" (MongoDB, Express.js, React.js, Node.js) stack capabilities.