In understanding the evolving digital landscape, one cannot overlook the significant role played by JavaScript developers. As catalysts fueling the interactive nature of the web, they wield the power to transform static HTML pages into dynamic interfaces, thereby enhancing user experiences across the web.

JavaScript, named after the Java language due to marketing considerations rather than technical similarities, was conceived by Brendan Eich at Netscape Communications in the mid-90s. It's a lightweight, interpreted scripting language with first-class functions. JavaScript is a prototype-based, multi-paradigm language that supports imperative, object-oriented, and declarative styles.

JavaScript developers are artisans of this scripting language, crafting patches of code to enhance website functionality and interactivity. They are the techno-magicians who animate the web, bringing elements to life with the conjuring power of JavaScript.

But what does the actual process of crafting an interactive web application entail? To understand this, we must journey into the world of JavaScript application development and the technologies involved.

Primarily, the cornerstone of any JavaScript application is HTML (Hyper Text Markup Language) and CSS (Cascading Style Sheets). HTML provides the basic structure of sites, which is enhanced and modified by CSS and JavaScript. While HTML is constituted of the bones of a web application, CSS is akin to the skin, determining the look and feel of the application. JavaScript, then, is the muscle, enabling the movement and interactivity within the application.

JavaScript developers employ a variety of libraries and frameworks to streamline their workflow and enhance the functionality of their applications. Libraries such as jQuery allow developers to write less code to accomplish more by simplifying tasks like HTML document traversal and manipulation, event handling, and animation.

Frameworks, on the other hand, provide a more comprehensive toolset for building applications. Angular, for example, is a powerful front-end framework developed by Google. It extends HTML's syntax to express components clearly and succinctly, while automatically syncing data between models and views, making development faster and testing easier.

React, a library for building user interfaces developed by Facebook, has gained massive popularity due to its unique approach of breaking down complex UI into simpler components. This enhances code reusability and makes the application easier to maintain and understand.

Despite the array of tools at their disposal, JavaScript developers must tread carefully when choosing what to incorporate into their projects. While using a robust, feature-rich framework like Angular might be advantageous for large-scale projects with complex requirements, it can be an unnecessary overhead for smaller applications where a simple library like jQuery is more than sufficient.

Moreover, the rapidly changing nature of the JavaScript ecosystem means that developers must always stay abreast of the latest technologies and trends. This can be both challenging and exciting, as the high rate of innovation often leads to significant improvements in the way applications are built and maintained.

A fundamental understanding of the underlying mathematical and computer science principles is also essential for JavaScript developers. Concepts such as algorithms, data structures, and computational complexity form the foundation upon which efficient and effective applications are built.

In conclusion, JavaScript developers are the architects of the modern web, shaping our digital experiences with their mastery of this versatile language. They hold the keys to a vibrant and interactive digital world, and their importance in this digital age is poised only to grow. From the economic perspective, they contribute significantly to the digital economy, with the proliferation of web applications expanding the boundaries of e-commerce and online businesses.

Unquestionably, the role of a JavaScript developer is complex, challenging, and multifaceted. It requires not only a deep understanding of the language itself, but also the ability to navigate the ever-changing landscape of technologies and frameworks that support its use. It requires a balance of creativity and logic, of innovation and adherence to best practices. Ultimately, the role is one of constant learning and evolution, mirroring the dynamic nature of the web itself.

So, as we marvel at the interactive capabilities of the web applications we use daily, let's give a nod to the JavaScript developers who make it possible. They are indeed the unsung heroes of the digital age.