Associate Consultant

React.js is an open-source JavaScript library that is used for building user interfaces specifically for single-page applications. It’s used for handling the view layer for web and mobile apps. React also allows us to create reusable UI components. React allows developers to create large web applications that can change data, without reloading the page. The main purpose of React is to be fast, scalable, and simple. It works only on user interfaces in the application. This corresponds to the view in the MVC template. It can be used with a combination of other JavaScript libraries or frameworks, such as Angular JS in MVC.

The virtual DOM (VDOM) is a programming concept where an ideal, or “virtual”, representation of a UI is kept in memory and synced with the “real” DOM by a library such as ReactDOM. This process is called reconciliation.
This approach enables the declarative API of React: You tell React what state you want the UI to be in, and it makes sure the DOM matches that state. This abstracts out the attribute manipulation, event handling, and manual DOM updating that you would otherwise have to use to build your app.

Hooks are the new feature introduced in the React 16.8 version. It allows you to use state and other React features without writing a class. Hooks are the functions which "hook into" React state and lifecycle features from function components. It does not work inside classes. Hooks are backward-compatible, which means it does not contain any breaking changes. Also, it does not replace your knowledge of React concepts.

When to use a Hooks : If you write a function component, and then you want to add some state to it, previously you do this by converting it to a class. But, now you can do it by using a Hook inside the existing function component.

Error Boundaries: Error Boundaries basically provide some sort of boundaries or checks on errors, They are React components that are used to handle JavaScript errors in their child component tree. React components that catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI. It catches errors during rendering, in lifecycle methods, etc.

Reason to Use: Suppose there is an error in JavaScript inside component then it used to corrupt React’s internal state and cause it to emit cryptic errors. Error boundaries help in removing these errors and display a Fallback UI instead(Which means a display of an error that something broke in the code).

As Node.js follows Single-Threaded with Event Loop Model inspired by JavaScript Event-based model with JavaScript callback mechanism. So, node.js is single-threaded similar to JavaScript but not purely JavaScript code which implies things that are done asynchronously like network calls, file system tasks, DNS lookup, etc.

Tip 1 : The cross questioning can go intense some time, think before you speak.

Tip 2 : Be open minded and answer whatever you are thinking, in these rounds I feel it is important to have opinion.

Tip 3 : Context of questions can be switched, pay attention to the details. It is okay to ask questions in these round, like what are the projects currently the company is investing, which team you are mentoring. How all is the work environment etc.