React JS is declarative because it allows developers to describe what they want the user interface (UI) to look like, rather than explicitly telling the computer how to create the UI. This is in contrast to imperative programming, which involves explicitly specifying each step of a program’s execution.
In React JS, developers create components that describe the UI based on the current state of the application. When the state of the application changes, React JS updates the UI automatically to reflect the new state. This is because React JS uses a virtual DOM, which is an in-memory representation of the actual DOM. When the state of the application changes, React JS updates the virtual DOM and then efficiently updates the actual DOM to reflect the changes.
By using a declarative programming style, React JS makes it easier for developers to write code that is easier to understand and maintain. Developers can focus on describing the desired UI, rather than worrying about the implementation details. This can also make it easier to debug and troubleshoot issues, since developers can more easily reason about the behavior of the application.
In addition to making development easier, React JS’s declarative programming style can also make it easier to optimize the performance of an application. Because React JS only updates the parts of the UI that need to be changed, rather than re-rendering the entire UI, it can be faster and more efficient than imperative approaches.
Overall, React JS is declarative because it allows developers to describe the desired UI, rather than explicitly specifying each step of the program’s execution. This makes it easier to write and maintain code, and can also lead to better performance.