Questions and answers

Here are some questions and answers to refresh your knowledge:

1. What is a side effect?

   A side effect is when a function relies on or modifies something outside of its input arguments. A very common side effect is the use of console.log inside a function.

2. What is useEffect?

   The useEffect hook is a way of defining a side effect callback to be invoked after a screen update in React. The effect can be invoked every time or when one of its dependencies changes. Therefore, the useEffect hook can be also used for listening for value changes.

3. What are the most common uses of useEffect?

   The useEffect hook is a common hook in the React family. If used along with the useState hook, it can easily communicate with external resources and bring results on screen. External resources can be web servers, DOM elements, window objects, document objects, or any third-party entities.