JSX is a syntax extension for JavaScript that allows developers to write HTML-like syntax in their JavaScript code. While JSX is the preferred way to write React components, it is not strictly required. React components can also be written using plain JavaScript syntax, although this can be more verbose and difficult to read. However, JSX is widely used in the React community and is considered a best practice for writing React components.

In React using ES6 classes, "super()" is used to call the constructor of the superclass, while "super(props)" is used to pass props to the constructor of the superclass. The "super(props)" syntax is necessary if you need to access props in the constructor of a subclass.

Render hijacking is a technique used in React where a component modifies the rendering behavior of its children by wrapping them in higher-order components (HOCs). This can be used to add or modify props, add event handlers, or manipulate the rendering of the children in other ways. While this can be a powerful technique, it can also lead to code that is difficult to reason about and maintain.

Redux DevTools is a browser extension and development tool that provides a visual interface for debugging and inspecting the state of a Redux application. It allows you to track and debug state changes, as well as inspect actions and reducers in real-time.

To enable production mode in React, you can set the NODE_ENV environment variable to "production". This will trigger various optimizations and remove development-only code from the bundle. You can also use the "process.env.NODE_ENV" variable in the code to conditionally enable certain features.

There are several ways to add Bootstrap to a React application, including installing the Bootstrap npm package and importing it into your components, linking to the Bootstrap CSS and JavaScript files in your HTML file, and using a third-party React Bootstrap library.

The strict mode feature in React is used to identify potential problems in code early on in the development process. It activates additional checks and warnings for common mistakes and unsafe operations, such as using deprecated lifecycle methods or modifying props directly. This can help prevent bugs and improve the overall quality of the code.

In React, you can pretty print JSON data by using the "JSON.stringify()" method with a "null" value for the "replacer" parameter and a number value for the "space" parameter. This will format the JSON data with indentation and line breaks for readability. For example: JSON.stringify(myData, null, 2).

Uncontrolled components are components that store their own state and are updated using refs. They are often used for simple form inputs, where managing the state in a parent component would be unnecessary overhead.

In React Router v4, you can implement a default or NotFound page by using a component to render the first matching child , and adding a as the last child. This route will match any path that has not been matched by other routes, and render the NotFound component.