LTIMindtree React Js Frontend Developer Interview Questions, Process, and Tips

A closure is a function that has access to its own scope, as well as the scope in which it was defined.

• A closure allows a function to access variables from its outer function even after the outer function has finished executing.

• Closures are created whenever a function is defined within another function.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { console.log(outerVa

Async/await is a feature in JavaScript that allows for asynchronous code to be written in a synchronous manner.

• Async/await is built on top of promises and provides a more readable and concise way to work with asynchronous code.

• The 'async' keyword is used to define a function as asynchronous, allowing it to use the 'await' keyword inside it.

• When 'await' is used, it pauses the execution of the function until the promise ...read more

Use Set to remove duplicates from array of strings.

• Create a Set from the array to automatically remove duplicates

• Convert the Set back to an array if needed

• Example: const arr = ['apple', 'banana', 'apple', 'orange']; const uniqueArr = [...new Set(arr)];

React DOM updates by comparing the virtual DOM with the actual DOM and only updating the necessary components.

• React creates a virtual DOM to represent the UI components.

• When a state or prop changes, React re-renders the virtual DOM.

• React then compares the virtual DOM with the actual DOM to identify the differences.

• Only the necessary components are updated in the actual DOM, minimizing performance impact.

React Hooks are functions that let you use state and other React features without writing a class.

• React Hooks were introduced in React 16.8.

• They allow you to use state and other React features in functional components.

• Some commonly used hooks are useState, useEffect, useContext, and useRef.

• Hooks make it easier to reuse logic across components.

• Hooks can be used to manage component state, perform side effects, and more.

Call, bind, and apply are methods used to manipulate the value of 'this' in JavaScript functions.

• Call - invokes a function with a specified 'this' value and arguments provided individually.

• Bind - creates a new function that, when called, has its 'this' keyword set to the provided value.

• Apply - invokes a function with a specified 'this' value and arguments provided as an array.

Redux Toolkit is a set of tools and best practices to simplify Redux development, while Redux is a predictable state container for JavaScript apps.

• Redux Toolkit provides a set of tools like createSlice, createAsyncThunk, and configureStore to simplify Redux setup and reduce boilerplate code.

• Redux Toolkit includes immer library for writing immutable update logic in a more convenient way.

• Redux Toolkit also includes a def...read more

Writing a RTL test to check a button in React

• Use the render and fireEvent functions from @testing-library/react

• Find the button element using getByRole('button')

• Simulate a click event using fireEvent.click

• Assert that the button is visible and clickable

Inline and block level elements are two types of HTML elements with different display behaviors.

• Inline elements flow in the same line as surrounding content, while block level elements take up the full width available.

• Examples of inline elements include <span>, <a>, and <strong>.

• Examples of block level elements include <div>, <p>, and <h1>.

Microtasks in JavaScript are tasks that are executed asynchronously and have higher priority than regular tasks.

• Microtasks are scheduled to run after the current script has finished but before the browser has a chance to render.

• They are often used with promises, as promise callbacks are executed as microtasks.

• Microtasks are executed in the same event loop iteration as regular tasks, but before the next rendering.

• Exampl...read more

Custom hooks are reusable functions that allow you to extract component logic into separate functions.

• Custom hooks are prefixed with 'use' and can call other hooks if needed.

• They can be used to share logic between components without duplicating code.

• Custom hooks can be created for any kind of logic, such as fetching data, managing state, or handling side effects.

Redux is a predictable state container for JavaScript apps. It helps manage the state of an application in a centralized store.

• Create a Redux store to hold the state of the application

• Define actions to describe state changes

• Write reducers to specify how the state changes in response to actions

• Dispatch actions to update the state in the store

• Connect components to the Redux store using the connect function from react-red

Redux is a predictable state container for JavaScript apps.

• Actions are dispatched to the store

• Reducers specify how the state changes in response to actions

• Store holds the state of the application

• Components can subscribe to the store to access state

Actual DOM represents the real structure of the web page, while Virtual DOM is a lightweight copy used for efficient updates.

• Actual DOM is the real structure of the web page that is directly manipulated by the browser.

• Virtual DOM is a lightweight copy of the Actual DOM that React uses for efficient updates.

• Changes made to the Virtual DOM are compared with the Actual DOM, and only the differences are updated in the Actu...read more