CleanMax Enviro Energy Solutions Senior Engineer Interview Questions and Answers for Freshers

Q1. What are the lifecycle methods?
Ans. 
Lifecycle methods are methods that are automatically called at certain points in the lifecycle of a component in React.
• Lifecycle methods include componentDidMount, componentDidUpdate, componentWillUnmount, etc.

• These methods allow developers to perform actions at specific points in a component's lifecycle, such as fetching data after the component has been rendered.

• They are used to manage side effects, perform cleanup, ...read more
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Q2. What are the advantages and features of react?
Ans. 
React is a popular JavaScript library for building user interfaces.
• Component-based architecture for reusability and easy maintenance

• Virtual DOM for efficient updates and performance optimization

• JSX syntax for writing HTML within JavaScript

• One-way data binding for predictable data flow

• Support for server-side rendering for improved SEO

• Large community and ecosystem with many third-party libraries and tools
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Q3. Difference between class and functional components?
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Class components are ES6 classes that extend from React.Component and have state and lifecycle methods, while functional components are simple functions that take props as input and return JSX.
• Class components are defined using ES6 classes and have a render method.

• Functional components are defined as simple functions that take props as input and return JSX.

• Class components can have state and lifecycle methods like comp...read more
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Q4. What are the Higher order components?
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Higher order components are functions that take a component and return a new component with additional functionality.
• Higher order components enhance the functionality of existing components

• They can be used for code reusability and separation of concerns

• Examples include withRouter from React Router and connect from React Redux
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Q5. What are the React hooks?
Ans. 
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 useReducer.

• Hooks are more flexible and easier to use compared to class components.
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Q6. What is the difference between contextAPI and Redux?
Ans. 
ContextAPI is a built-in feature in React for managing global state, while Redux is a separate library for state management in React applications.
• ContextAPI is built into React, while Redux is a separate library.

• ContextAPI is primarily used for managing global state in a React application.

• Redux provides a centralized store for state management and follows a unidirectional data flow.

• ContextAPI is simpler to use for smal...read more
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Q7. What are the semantic elements in html?
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Semantic elements in HTML are tags that clearly define the content they wrap, providing meaning to both browsers and developers.
• Semantic elements help improve SEO by providing search engines with better understanding of the content.

• Examples of semantic elements include <header>, <footer>, <article>, <section>, <nav>, <aside>, <main>, <figure>, <figcaption>, <deta...read more
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Q8. What are the pseudo elements?
Ans. 
Pseudo elements are used in CSS to style specific parts of an element.
• Pseudo elements are denoted by double colons (::) in CSS.

• They allow styling of specific parts of an element, like the first letter or line.

• Common pseudo elements include ::before, ::after, ::first-line, and ::first-letter.
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Q9. What is box model?
Ans. 
The box model is a fundamental concept in CSS that defines the layout of elements on a webpage.
• The box model consists of content, padding, border, and margin.

• Content: the actual content of the element, such as text or images.

• Padding: space between the content and the border.

• Border: a line that goes around the padding and content.

• Margin: space outside the border, separating the element from other elements.
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Q10. What is hoisting?
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Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during the compilation phase.
• Variable and function declarations are hoisted to the top of their scope.

• Only declarations are hoisted, not initializations.

• Function declarations take precedence over variable declarations.

• Example: console.log(myVar); var myVar = 10; // Output: undefined

• Example: cons...read more
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Q11. What is difference between normal function and arrow function?
Ans. 
Normal functions are defined using the function keyword, while arrow functions are defined using the => syntax.
• Normal functions are hoisted, while arrow functions are not hoisted.

• Arrow functions do not have their own 'this' keyword, they inherit it from the parent scope.

• Arrow functions do not have their own 'arguments' object.

• Arrow functions are more concise and have implicit return.

• Arrow functions cannot be used as co
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Q12. What is splice and slice?
Ans. 
Splice and slice are methods used in programming to manipulate arrays.
• Splice is used to add or remove elements from an array at a specific index.

• Slice is used to extract a portion of an array and returns a new array.

• Example of splice: array.splice(2, 0, 'new element') - adds 'new element' at index 2.

• Example of slice: array.slice(1, 4) - extracts elements from index 1 to 3.
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Coding questions on Java script like array methods and objects handling. coding questions on React is like life cycle methods using functional components and state management.

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