React's state triggers render every time it changes. This property allows the implementation of many different features, including tons of custom UI components such as popovers, tooltips, accordions, etc. Popular UI libraries for React use this concept extensively for their components.
This guide explores the simplest way to implement a "read more" link in a React app.
Remember to break the entire code into modular and reusable components. Feel free to customize this feature as per the needs of your app. If you intend to show only text, you can render this component inside a card already holding some truncated content. In some cases, instead of rendering a link, you can render it as a Show More button. If you want to make a custom accordion or an expanded menu on the navbar, you can use the same concept of conditional rendering along with some CSS touch up.
"Read more" links are common these days and can be easily implemented using conditional rendering, as explained in this guide. You can also use several React packages for the same purpose, but using a library for such a task seems like overkill. Implementing components using some well-defined logic not only widens the learning horizons of a developer, but also mkeeps the app free from unnecessary packages and libraries. As an exercise, you can try figuring out a neat CSS hack to do something similar.