Top 5 Interview Questions for Beginner React Developers

Are you preparing yourself for a React interview? Search no further. This article is all about the top 5 React interview questions that beginners should be prepared to answer. This article will be necessary for those who will face a junior/senior React developer interview. Before shedding light on those commonly-asked React interview questions, let us discuss some basic aspects of React JavaScript.

According to many (including Stack Overflow) surveys, the React library is still the most used and popular library among the other available JavaScript libraries. React has exploded in popularity because its simple and declarative API produces highly performant applications — and that momentum only continues to grow. If you’re looking to build a robust web application, chances are that React may be a good fit for you. Once you're ready to hire a React developer, here are essential interview questions to ask and some advanced concepts to know.

Some Advice on Technical Interviews

Before we jump deep into this article, you must know that technical interviews are infamous for gotcha-style topics and irrelevant whiteboarding practices. I am not gonna talk about the interview style at all in this article — rather, I’ll discuss the top 5 interview questions for beginner React developers.

1. What is React JS? How do you distinguish it from other JavaScript frameworks?

It might sound like a naive question, but the hiring managers often prefer to hear the answer from candidates. This is the most asked question to candidates. Based upon this question, board members expect an informed opinion about React, as well as any competing alternatives. In simple words, this question is designed to examine a candidate's knowledge about the JavaScript ecosystem at large while also pressing for specifics on what makes React different from others. Your answer should be clear and on the point.

“React is an open-source JavaScript library designed by Facebook for building complex, interactive UIs in web and mobile applications. It was created in 2011”

Coming back to the second part of the question. In this portion of the question, the manager expects to hear the answer based on your experiences. The question-answer may vary, from candidate to candidate. However, the best answer should be:

“React is a small library focused on building UI components, it is necessarily different from a lot of other JavaScript frameworks. For instance, AngularJS proposes building an application by extending HTML markup and adding various constructs at runtime. On the other hand, React concentrates completely on the making of components, and it has few evaluations about an application’s architecture.”

2. What do you know about JSX?

“JSX is a shorthand for JavaScript XML. JSX is a type of file used by React that utilizes the expressiveness of JavaScript along with HTML, like template syntax. This makes the HTML file easy to comprehend. This file makes applications robust and boosts their performance.”

Provide a sample code snippet along with the definition of JSX. It will force them to think positively about you. For instance:

class TestComponent extends React.Component {
  render() {
    let props = this.props;
    return (
      <div className="test-component">
        <a href={props.url}>{props.name}</a>
      </div> 
    );
  } 
}

Note: JSX code by itself cannot be read by the browser; it must be transpired into traditional JavaScript using tools like Babel and webpack.

3. What is Redux? Could you give us an implementation of it?

Redux is a library that’s compatible with and complementary to React, so it’s important to have enough understanding to be conversant about it in a React job interview. Your answer could be:

“Dan Abramov and Andrew Clark designed Redux, a lightweight state management tool used for JavaScript applications, and it was published in 2015. For JavaScript and React applications, Redux is a standard data store. Data binding should move in one direction and should be saved as a single source of truth; this was according to the basic concept. The popularity of Redux stems from the design concept's simplicity and the fact that it is reasonably easy to apply.”

Example of Reducers in Redux:

Reducers are simple functions that take an application's current state, execute an action, and return a new state. These states are objects that specify how an application's state changes in response to an action made to the store.

It is based on the reduce function in JavaScript, which calculates a single value from many values following the execution of a callback function.

Here's an illustration of how Redux reducers work:

const LoginComponent = (state = initialState, action) => {
    switch (action.type) {
        case "LOGIN":
            return state.map(user => {
                if (user.username !== action.username) {
                    return user;
                }
                if (user.password == action.password) {
                    return {
                        ...user,
                        login_status: "LOGGED IN"

                    }
                }
            });
        default:
            return state;
    }
};

What are React components? What is a state in React?

When it comes to using React, everything boils down to components. In simple words, “Components are the construction blocks of a React application’s UI. These components split up the entire UI into several small, independent, and reusable pieces. Then it renders each of these components independent of each other without affecting the rest of the UI.”

Then again, “States are the heart of React components. States are the source of data and must be kept as simple as possible. Basically, states are the objects which determine components rendering and behavior. They are mutable unlike the props and create dynamic and interactive components. They are accessed via this.state().”

5. What are stateless components?

“Stateless components are nothing more than pure functions that render DOM-based solely on the properties provided to them. They do not have the authority to change the state.” A relative example is given below:

const StatelessCmp = props => {
    return (
      <div className="my-stateless-component">
        {props.name}: {props.birthday}
      </div>
    ); 
};
ReactDOM.render(
    <StatelessCmp name="Art" birthday="10/01/1980" />,
    document.getElementById('main')
);

Wrapping Up

When you are facing a hiring manager, DO NOT get nervous and hesitate to answer. I repeat, DO NOT mess up your answers. Stick to the answer and keep expressing what you believe in regarding your prior experience.