In today’s competitive web development world, HTML, CSS, JavaScript, ReactJS and NodeJS are necessary fundamental. Whether it’s the first job interview or the preparation for an advanced position, here are 5 interview questions and answers for every technology chosen by a professional to ensure success.
📈 HTML - Interview Questions and Answers
1. What is HTML and why is it used in web development?
Answer: HTML (HyperText Markup Language) is the standard language used to create the structure of web pages. It provides a way to format and organize content using elements like headings, paragraphs, images, and links.
2. What is the difference between <div> and <span> tags?
Answer: <div> is a block-level element used to group large chunks of code or elements, whereas <span> is an inline element used for small portions of content like styling a word within a paragraph.
3. What are semantic HTML elements? Give examples.
Answer: Semantic elements clearly describe their meaning in a human- and machine-readable way. Examples: <article>, <section>, <header>, <footer>.
4. How do you create a form in HTML?
Answer: A form is created using the <form> tag. Inside it, various input types like text, email, password, and submit buttons can be used:
🌈 CSS - Interview Questions and Answers
1. What is the difference between ID and Class in CSS?
Answer: ID is unique and used to style a single element (#id). Class can be reused on multiple elements (.class).
2. Explain the Box Model in CSS.
Answer: The box model consists of: Content → Padding → Border → Margin. It defines how elements are spaced and sized.
3. What is specificity in CSS and how is it calculated?
Answer: Specificity determines which CSS rule is applied when multiple rules match the same element. Inline styles > IDs > Classes > Elements.
4. How does Flexbox work?
Answer: Flexbox is a layout model that allows easy alignment of items in a container. Example:
5. What are media queries in CSS?
Answer: Media queries make a website responsive by applying styles based on screen size or device type.
🧬 JavaScript - Interview Questions and Answers
1. What are variables in JavaScript?
Answer: Variables store data. var is function-scoped, let and const are block-scoped. const cannot be reassigned.
2. What is the difference between == and ===?
Answer: == compares values after type conversion, while === compares both value and type strictly.
3. What is a closure in JavaScript?
Answer: A closure is a function that remembers its lexical scope even after the parent function has finished execution.
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| Example |
4. Explain the concept of hoisting.
Answer: Hoisting moves variable and function declarations to the top of their scope before code execution, but not their assignments.
5. What are Promises in JavaScript?
Answer: Promises handle asynchronous operations. They have three states: pending, resolved, and rejected.
fetch('api/data')
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.log(error));🪄 ReactJS - Interview Questions and Answers
1. What is React and why is it used?
Answer: React is a JavaScript library for building user interfaces, especially for single-page applications. It allows for reusable components and efficient DOM updates.
2. What is JSX?
Answer: JSX stands for JavaScript XML. It allows writing HTML-like code in JavaScript and is used to describe UI components in React.
3. Difference between functional and class components?
Answer: Functional components are simpler and use hooks, while class components use lifecycle methods and this keyword.
4. What are props and state in React?
Answer: Props are inputs to components (read-only). State is a built-in object used to hold data that changes over time.
5. What is the useEffect() hook?
Answer: useEffect() performs side effects in functional components, like fetching data or updating the DOM after render.
🧲 NodeJS - Interview Questions and Answers
1. What is NodeJS and its use?
Answer: NodeJS is a JavaScript runtime environment that executes JavaScript code outside the browser. It is used for server-side development.
2. What is the difference between synchronous and asynchronous in NodeJS?
Answer: Synchronous blocks execution until tasks complete. Asynchronous allows multiple tasks to run without waiting for others.
3. Name some core modules in NodeJS.
Answer: Common core modules include http, fs, path, events, and os.
4. What is ExpressJS?
Answer: Express is a NodeJS web application framework that simplifies building APIs and web apps using middleware and routing.
5. How does the Event Loop work in NodeJS?
Answer: The Event Loop handles asynchronous callbacks. It listens for events and processes them one by one in a non-blocking manner.
Conclusion:
Mastering these five core technologies — HTML, CSS, JavaScript, ReactJS, and NodeJS — gives you the confidence to tackle most front-end and back-end interview questions. These Q&As offer a strong foundation to demonstrate your technical knowledge and problem-solving ability in real interviews.
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