Introduction

Interview questions for senior react JS developers are designed to test both the understanding and practical application of react JS by senior developers. Given that react has been in use since 2013, interviewers believe it is a developer favorite. Pretty good interview questions have been developed around this Javascript library to test how much of React a senior developer knows.

 

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A Little React History

 

 

Developed by Facebook in 2011, React is a declarative, efficient, and flexible JavaScript library for building user interfaces. As a frontend tool, react lets developers write complex UIs from small, isolated code called “components.”

 

The birth of React JS was motivated by the need for flawless coding procedures: In 2011, the developers behind the Facebook brand started having issues with code maintenance. This was due to the growing number of features on the Facebook Ad app. 

 

Over time, their app became slow and lagged as they faced a lot of cascading updates.

After a while, senior developers at Facebook couldn’t bear the laxity and countless never-ending updates. 

 

This was a call for upgrading codes and coding systems for efficiency and speed. Trust the brilliant developers at Facebook; they came up with the perfect model but needed to make the User experience just right.

 

Jordan Walke came to the rescue and built a prototype that made the process more efficient. This marked the epic birth of React JS- every developer’s favorite library. 

 

This article highlights the skills every senior react js developer should have and the top interview questions to expect as a senior-level developer using react Js.

 

Ready to be prepped for the next big role as a senior developer? 

 

Skills To Expect From A Senior React Js Developer

Even as you source tech-talent from the different pools available, you must know what to expect from the right ones. Their knowledge of the react structure and how to navigate through it isn't enough. As a react developer in this century, they must be well versed in other react-related skills. As an interviewer, you expect that they already know this and that they have hands-on experience with these skills. The expectations are higher if you’re interviewing for a senior developer role.

 

Here are five top skills every senior developer using the react JS library should know:

 

1.  HTML + CSS

2. Node + npm

3. JavaScript Fundamentals + ES6

4. Git

5. Redux

1. HTML+CSS

Every developer should have a background in HTML and CSS. Front-end developers should be even more versed in the techniques of HTML and CSS. 

 

HTML, an acronym for Hypertext Markup Language, and CSS, an acronym for Cascading Style Sheets, are two important coding techniques needed to build Web pages. 

 

HTML allows developers design the page structure, while CSS makes for the visual and aural layout for the different devices where the webpage would be displayed. 

 

Understanding and applying HTML+CSS is the most basic knowledge every developer needs for building Web pages and Web Applications.

 

As an interviewer, you'd expect that Senior react JS developers can write and apply semantic HTML tags, implement a CSS reset, understand the box model and know how to reset to border-box, and understand flexbox. 

 

2. Node + npm

Node and npm might seem unnecessary, but they are important skill sets developers should have up their sleeves as they are looking to impress. 

 

Node is a framework built to run JavaScript code on your device, while npm works like a  package manager, working to install and uninstall javascript packages- node modules.

 

As a package manager, npm holds lots of software to help other developers develop new software. It's like a scrap yard for engineers, just that this scrap yard isn't trashy and all.

 

3.JavaScript Fundamentals + ES6

Interview questions for senior react JS developers often open with brushing up on the Javascript fundamentals. ES6, on the other hand, comes with new keywords that simplify the Javascript process. 

 

A react JS senior developer should be used to Javascript fundamentals like variables and scoping, arrays and objects, array methods, function and arrow functions, DOM manipulation, event handlers, ‘this’ keyword, higher-order functions, callback functions, prototypal inheritance, object creation, e.t.c;

 

4. Git

Every developer, beginner, mid-level, or senior, should know GIT. Well, this is because of all the benefits you get on the Github, Gitlab, and Bitbucket platforms as you grow in your developer career.

 

The perfect developer's Git skills should include and maybe exceed tracking changes with add, commit, push and pull, branching and merging strategies, and handling merge conflicts.

 

5. Redux

Redux is a safe spot for react developers. Why? Well, turns out React comes with state management. 

 

Developers have been disappointed countless times when they discovered the asynchronicity of state updates and how React handles them. To help developers and for scalability, Redux was built.

 

Redux is more of a state management library and less of a framework. It is an opinionated way of working with data. 

 

The principles that govern Redux tally with the principles of functional programming and immutability, and developers have the liberty to carve their path. However, they must be masters of the concepts of fundamental React programming before trying out Redux.

 

Your ideal senior developer should know this.

 

5 Strategic Interview Questions for Senior React JS Developers

Different interviewers and interview panels have different interview questions for the same role. Interview questions also relate to company objectives and how much experience they already have in the tech sector. This is to say that the questions below are not a one-cap-fits-all kind.

 

We are, however, certain that interview questions for every senior developer role will cut across the five strategic questions for Senior React JS Developers as highlighted below:

 

1. How To Optimize a React application to improve its performance? 

It is expected that senior React developers ought to know how to optimize a React application for better performance. 

 

You can ascertain this pretty easy if you pay attention to their understanding of React’s lifecycle and hooks. 

 

Developers can optimize a React app’s performance in the following ways:

 

1. Avoid unnecessary rerenders

2. Use a unique identifier (UID) when rendering lists

3. Apply hooks such as useMemo and use callback for expense functions

4. Mount checks as you progress.

 

2. How Do You Properly Handle Complex Data Structures in a React Application? 

 

From time to time, developers will be expected to work with complex data structures in React. To do this successfully, they will need to use their mapping over nested data skill. It is your responsibility as a recruiter to confirm if they know this. 

 

They might also need to use recursive components to render data with multiple levels of nesting. Knowing how to optimize performance with React.memo will be a plus.

 

You should also check that they can use utility libraries such as lodash to manipulate and transform complex data structures.

 

The fact is that there are many ways to handle complex data structures in React. But does your prospective developer know this?

 

3. How Do You Handle Asynchronous Actions In A React Application?

The obvious response to this question is to use the async and await keywords, which allow developers to write asynchronous code in a synchronous-looking style.

 

There’s another way, however: using a library like axios or fetch to make API calls. Give your prospect an extra point if they know this.

 

4. Discuss the Difference Between a Presentational and Container component in React?

 

As their names imply,  presentational components relate to how things look, while container components are concerned with how things work.

 

Presentational components render user interface elements to the screen, are usually focused on rendering JSX, and are not aware of the app’s state or actions.

Container components exist to manage states and actions. They are class-based components,  contain the logic for fetching data, handling user input, and performing other tasks, are aware of the app’s state, and pass data and callbacks to presentational components as props.

 

5. How Do You Handle Client-Side Routing In A React Application?

Developers can handle client-side routing in a React app in different ways. It is easier to use the react-router-dom library.

 

The react-router-dom library provides a <Router> component for routing and a set of <Route> components for defining the routes in your app.

 

Here’s an example of how they could use react-router-dom to handle client-side routing in a React app:

 

• Install the react-router-dom library.

 

• npm install react-router-dom

 

• Import the <Router> and <Route> components from react-router-dom.

 

• import { BrowserRouter as Router, Route } from 'react-router-dom';

 

• Wrap your app with the <Router> component.

 

• <Router>

 

•  <App />

 

• </Router>

 

• Define your routes using the <Route> component. 

 

The <Route> component takes a path prop that specifies the path for the route and a component prop that specifies the component to render when the route is matched.

 

Conclusion

These questions are basic, yet need the right answers if you want your company to move hitch-free for the next year. You can only tolerate excellence in your hiring process.

 

We hope you understand that there are more than five interview questions for Senior react JS developers, though.

But, why bother yourself with these, when you can have the perfect developer on your project at the snap of a finger?

See you in the next article!