Vanilla.JS vs jQuery UI: What are the differences?

## Introduction
In this comparison, we will explore the key differences between Vanilla.JS and jQuery UI.

1. **Syntax**: Vanilla.JS uses plain JavaScript syntax while jQuery UI is a library built on top of jQuery, providing its own syntax and methods. 
2. **DOM Manipulation**: Vanilla.JS allows direct manipulation of the DOM through JavaScript while jQuery UI simplifies DOM manipulation with its built-in methods like `.append()`, `.remove()`, etc.
3. **File Size**: Vanilla.JS is a lightweight library as it consists of pure JavaScript code leading to smaller file sizes, whereas jQuery UI is a larger library due to the additional functionalities it offers.
4. **Browser Compatibility**: Vanilla.JS ensures better browser compatibility as it solely relies on standard JavaScript features, whereas jQuery UI might have more consistent behavior across different browsers due to its abstraction layer.
5. **Learning Curve**: Vanilla.JS is the fundamental JavaScript language, making it essential for developers to have a strong understanding of JavaScript concepts, while jQuery UI provides a higher level of abstraction making it easier to learn and use for beginners.
6. **Performance**: Vanilla.JS may have better performance since it directly interacts with the browser's native functionality, whereas jQuery UI may introduce some overhead due to its library functions.

In Summary, the key differences between Vanilla.JS and jQuery UI lie in syntax, DOM manipulation, file size, browser compatibility, learning curve, and performance.