EPAM Systems Reactjs Developer Interview Questions and Answers

Use media queries, flexible grids, and relative units to create a responsive web page.

• Use media queries to apply different styles based on screen size

• Create flexible grids using CSS Grid or Flexbox

• Use relative units like percentages or ems for sizing elements

• Consider using frameworks like Bootstrap or Material-UI for responsive design

• Test your design on different devices and screen sizes

SASS is a preprocessor scripting language that is interpreted into CSS, offering more features and flexibility.

• SASS is a preprocessor for CSS, allowing for variables, nesting, and mixins to be used in stylesheets.

• SASS code needs to be compiled into CSS before being used in a web project.

• SASS helps in writing cleaner and more organized CSS code, making it easier to maintain and update styles.

• CSS is the styling language ...read more

Form validation using HTML and validating phone number with country code

• Use HTML5 form validation attributes like 'required', 'pattern', 'minlength', etc.

• For phone number validation, use 'pattern' attribute with regex for specific country code format

• Example: <input type='tel' pattern='[0-9]{3}-[0-9]{3}-[0-9]{4}' required>

I use Jest for testing React applications due to its simplicity and integration with React ecosystem.

• Jest is the most popular test library for React applications

• It comes pre-configured with Create React App and has great support for snapshot testing

• Jest also has built-in mocking capabilities which make it easy to test components with dependencies

Mounting is the process of rendering a component into the DOM, while shallow rendering allows testing a component without rendering its children.

• Mounting is the initial phase of the component lifecycle where the component is rendered into the DOM.

• Shallow rendering in testing library renders only the component itself, not its children.

• Shallow rendering is useful for isolating the component being tested and avoiding rend...read more

Redux Toolkit is the official, recommended way to write Redux logic. It simplifies the process of managing state in React applications.

• Redux Toolkit provides a set of tools and best practices to streamline Redux development.

• It includes utilities like createSlice, createReducer, and configureStore to simplify the code and reduce boilerplate.

• Redux Toolkit also includes built-in Immer integration for writing immutable upd...read more

API calls in Redux are typically handled using middleware like Redux Thunk. User name can be retrieved from Redux state and displayed in components.

• Use Redux Thunk middleware to make API calls in Redux

• Dispatch actions to update Redux state with API response data

• Access user name from Redux state in components to display it

Thunk middleware in Redux allows for asynchronous logic to be handled in Redux actions.

• Thunk middleware allows for dispatching functions instead of just plain objects in Redux actions.

• It enables handling asynchronous API calls within Redux actions.

• Thunk middleware helps in simplifying the code by moving complex logic outside of components.

• Example: Thunk middleware can be used to dispatch an action after a delay or to f...read more