Best Front-end Developer Interview Questions And Answers

As an entrepreneur, project manager, or CTO, you know that finding the right developers is the key to your project’s success. Hence the importance of having a well-mapped process for hiring software developers. In the above code, you can see that when the counterValue equals 2, it throws an error inside the render method.

This method decides the re-rendering of the component by returning a boolean value . In React.Component, shouldComponentUpdate() method returns true by default. But in React.PureComponent, it compares the changes in state or props to re-render the Front-end Developer React job component. The pure component enhances the simplicity of the code and performance of the application. Catching potential problems is a huge benefit when building applications. React has a built-in component to help developers do just that.

React Interview Questions and Answers

ComponentWillMount()– Executed just before rendering takes place both on the client as well as server-side. Browsers can only read JavaScript objects but JSX in not a regular JavaScript https://wizardsdev.com/ object. Thus to enable a browser to read JSX, first, we need to transform JSX file into a JavaScript object using JSX transformers like Babel and then pass it to the browser.

Oftentimes, you will need to pass data between the components as you go down the tree. HR managers have a limited amount of time to evaluate the technical knowledge and practical experience of a candidate. When building a React application, it’s common to need to respond to user actions such as button clicks, form submissions, and other events.

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Class components are more complex than function components, but provide more advanced features. A “pure component” in React is a component that updates only when its properties or state have changed. In contrast, a “non-pure component” re-renders each time the parent component re-renders, regardless of whether its props or state have changed. Pure components are more productive since they do not needlessly re-render. This prompts the shouldComponentUpdate method, which decides whether or not to re-render, to provide an automatic shallow comparison of the component’s props and state.

By using JSX, we can write HTML structures in the same file that contains JavaScript code. ● In MVC Frameworks, applications are comparatively slower and more inefficient than other alternatives of MVC Framework. React Routing uses a single HTML Page for multiple views whereas Conventional Routing creates a different file for different views. Arrow functions are used when high-order functions are being implemented. Arrow Function enables use to bind the component’s context because ReactJS uses ES6 and it doesn’t have auto binding enabled by default.

How can you create a component in React?

ThesetStatefunction is the recommended approach to update the state object as React does the heavy lifting for you. Keeping your views and your logic in sync is an important aspect of every application. This is equivalent to updating the state object and making sure the component is updated accordingly. The candidate should be able to explain the recommended approach when working with the state object and how to avoid the component from getting out of sync with the state. Stateless components (a flavor of “reusable” components) are nothing more than pure functions that render DOM-based solely on the properties provided to them.

By using the React Profiler, performance can be measured before and after using these tools to ensure that performance is actually improved by making a given change. One of the most commonly asked questions that I’ve seen in front-end interview rounds is to create a custom hook for keyboard events. Connected components are higher-order components that are wrapped around plain components to provide them access to the Redux store. Connected components are used to access the state of the store and dispatch actions, whereas plain components are used to manage UI elements and local component state. Used to display UI elements, manage local component state and pass props to child components. A Custom Hook in React is a JavaScript function that lets you extract state logic and behavior out of a component, and reuse it across multiple components.

React Developer Qualifications

The state is very similar to props, but it is private and fully controlled by the component. I.e., It is not accessible to any other component till the owner component decides to pass it. If you want a web browser to read a JSX file, you must transform the files into a regular JavaScript object. This is because the web browsers are built to read the regular JS objects only, and JSX is not a regular JavaScript object. In React, it is necessary to start component names with a capital letter. If we start the component name with lower case, it will throw an error as an unrecognized tag.

So, they must collaborate with your development team leader or tech lead. They can both work together in crafting technical exams and interview questions. Flux is an application architecture that Facebook uses internally for building the client-side web application with React. It is a kind of architecture that complements React as view and follows the concept of Unidirectional Data Flow model. It is useful when the project has dynamic data, and we need to keep the data updated in an effective manner. You should call hooks only at the top level of your React functions and not inside the loops, conditions, or nested functions.

Stateless components are typically used for simple, presentational elements that don’t need to handle any complex logic or internal state updates. React’s render function creates a node tree out of the React components. It then updates this tree in response to the mutations in the data model which is caused by various actions done by the user or by the system. Check out this Web developer course online to learn more about react.

• ComponentDidMount()–Executed on the client side only after the first render.
• These middleware provide a way to handle the asynchrony of the operation and ensure that the state is updated appropriately once the operation is complete.
• It’s always a good idea to test performance with real-world use cases and user interactions before and after making any optimization.
• Validation helps to catch potential errors early in the development process and prevent bugs from affecting the end-user experience.
• This whole optimization process significantly reduces the web application load time, thereby making it more efficient.