IBM ReactJs Interview - Fresher | 🎉 Selected | ReactJs & Javascript #reactinterviewquestions #ibm

Summary

The script delves into web development topics, contrasting local and session storage, emphasizing React's popularity due to its virtual DOM, one-way data binding, and component-based architecture. It also covers Redux for state management, TypeScript basics, and the distinction between 'type' and 'interface'. Practical examples include using React fragments, differentiating 'map' and 'forEach', and employing 'this' keyword. Additionally, it demonstrates creating a React input box with age validation and error messaging, showcasing coding practices and React functionalities.

Takeaways

• 📝 Local Storage and Session Storage are both browser storage options, with Local Storage persisting data until manually deleted and Session Storage clearing data upon tab closure.
• 🗂️ Local and Session Storage can each store up to 10 MB of data, with Local Storage being session-independent and Session Storage being session-specific.
• 🔥 React's popularity is attributed to its use of the Virtual DOM, which improves performance by only updating the necessary parts of the UI instead of re-rendering the entire interface.
• 🔄 React's one-way data binding simplifies debugging by ensuring data flows in a single direction, making it easier to trace and manage.
• 🧱 React's component-based architecture allows for the creation of reusable components, enhancing modularity and maintainability in applications.
• 📚 JSX, used in React, provides an HTML-like syntax that is familiar to developers, making it easier to write and understand code.
• 📁 The speaker's preferred project folder structure includes folders for containers, components, store logic, helpers, config, and hooks, promoting organization and reusability.
• 🔄 React Fragments are used to wrap multiple children in a single component without adding extra nodes to the DOM, which would otherwise cause errors.
• 🚫 The difference between state and props is highlighted by state being mutable and used for dynamic component changes, while props are immutable and used for data passing between components.
• 🔑 The use of 'useMemo' and 'useCallback' hooks in React is to optimize performance by memorizing computed values and preventing unnecessary re-renders, respectively.
• 🛠 Redux is a state management tool that centralizes application state in a single store, with a clear flow of actions and reducers to handle state updates and side effects.

Q & A

What is the primary difference between local storage and session storage in web browsers?

Local storage retains data until it is manually deleted, while session storage data is cleared when the browser tab is closed.

How much data can be stored in both local storage and session storage?

Both local storage and session storage can store up to 10 MB of data.

What is the main reason behind React's popularity?

React's popularity is primarily due to its use of the virtual DOM, which improves performance by only updating the parts of the UI that change, instead of re-rendering the entire UI.

What is one-way binding in React and why is it beneficial for debugging?

One-way binding in React allows data to flow only from parent to child, making it easier to debug because the data flow is unidirectional and more predictable.

How does the component-based architecture in React contribute to code reusability?

In React, everything is a component, which means that individual components like buttons, search bars, or image sections can be reused across different parts of an application.

What is JSX in React and why is it beneficial for developers familiar with HTML and JavaScript?

JSX is an HTML-like syntax used in React that allows developers who are familiar with HTML and JavaScript to easily write components.

Can you describe the typical folder structure used in a React project according to the transcript?

The typical folder structure includes folders like 'store' for Redux logic, 'helpers' for reusable methods, 'hooks' for custom hooks, 'components' for presentational components, and 'containers' for components that manage state and access Redux data.

What is a React Fragment and why is it used?

A React Fragment is an empty tag used to wrap multiple children in a component's render method without adding extra nodes to the DOM, which would otherwise throw an error for requiring a single parent element.

What is the difference between 'state' and 'props' in React components?

'State' is mutable and used for rendering dynamic changes within a component, while 'props' are immutable and used to pass data between components.

How does the use of 'useState' differ from 'useProps' in React functional components?

'useState' is used to add state to functional components, whereas 'useProps' is not a standard React hook; the term might be a confusion with 'props' which are the properties passed to a component.

What is the purpose of 'useMemo' and 'useCallback' hooks in React?

'useMemo' is used to avoid recalculating complex calculations by memorizing the previously computed value, while 'useCallback' is used to prevent unnecessary re-renders by avoiding the creation of new callback instances unless required.

Can you explain the concept of Redux and its basic workflow?

Redux is used to manage the state at the top level of an application with a single store. Components can read from this store, and changes are made through actions and reducers. Actions send an action type and payload, which reducers then process to update the store. Redux also provides developer tools for easy debugging of state changes.

What is the basic difference between 'type' and 'interface' in TypeScript?

'Type' in TypeScript is used to define unions, tuples, and intersections, while 'interface' is used to describe the shape of objects and function declarations.

How do 'map' and 'forEach' differ in JavaScript when used with arrays?

'map' returns a new array with the results of the callback function for each element, whereas 'forEach' iterates over each element but does not return a new array and mutates the original array.

What does the 'this' keyword refer to in JavaScript and can you provide a simple example?

The 'this' keyword refers to the object that is executing the current code. For example, in an object with a method, 'this' inside that method refers to the object itself.

How can you create an age input box in React that displays an error message if the age is less than 18?

You can create a controlled input component with state to store the entered age and another state to track error messages. Use an onChange event to update the state and validate the age, setting an error state if the age is less than 18 and displaying the error message accordingly.