ReactJS Interview and Prep: Top 11 Questions and Answers

1. What happens with a component when it receives new props?

• The component will update. A component updates when it receives new props or state, usually in response to an interaction.

2. Describe how to use useState

• useState is a React hook that lets you add a state variable to your component in functional components. You pass the initial state to this function, and it returns a variable with the current state value (not necessarily the initial state) and another function to update this value.
• useState is equivalent of this state / this.setState for functional components

const [state, setState] = useState(initialState)

3. How can you share a state between multiple components?

• Parent to child: Props or instance methods
• Child to parent: Callback functions or event bubbling. Callback function is a function which is to be executed after another function has finished execution.
• Sibling to sibling: Parent component (lifting state up)
• Any to any: Observer Pattern, Global variables or Context

4. Do you have to use React with JSX?

No. JSX is not a requirement for using React. Using React without JSX is convenient when you don’t want to set up compilation in your build environment.