Basic JavaScript Questions
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2. Explain the difference between "null" and "undefined" in JavaScript.
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3. How do you declare a variable in JavaScript?
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4. What are the different data types in JavaScript?
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5. How do you check the data type of a variable?
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6. What is a closure in JavaScript?
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7. Explain the concept of hoisting in JavaScript.
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8. What is the difference between "==" and "===" operators in JavaScript?
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9. How do you comment in JavaScript?
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10. Explain the purpose of the "use strict" directive.
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Intermediate JavaScript Questions
- What is the DOM, and how do you manipulate it using JavaScript?
- Explain the concept of event delegation.
- What is a callback function, and why is it used in JavaScript?
- What is the difference between "null" and "undefined" in JavaScript?
- Describe the purpose of "this" in JavaScript and how it is determined.
- How does prototypal inheritance work in JavaScript?
- What are promises in JavaScript, and how do they work?
- Explain what "async/await" is and how it works.
- How can you handle errors in JavaScript?
- What is the difference between "let," "const," and "var" when declaring variables.
Advanced JavaScript Questions
- What is the event loop in JavaScript, and how does it work?
- Explain the differences between "setTimeout" and "setInterval."
- How does the module system work in JavaScript (e.g., CommonJS, ES6 modules)?
- What is the difference between "map," "filter," and "reduce" in JavaScript?
- Explain the concept of "closures."
- What is memoization in JavaScript?
- How does the "spread" operator work in JavaScript?
- What are generators and how do they work?
- Describe the concept of functional programming in JavaScript.
- How can you avoid callback hell (Pyramid of Doom) in JavaScript?
DOM and Web API Questions
- How do you create an element in the DOM using JavaScript?
- Explain the difference between "clientHeight," "offsetHeight," and "scrollHeight."
- How do you add an event listener to an element in the DOM?
- What is the purpose of the XMLHttpRequest object in JavaScript?
- How can you make an HTTP request in JavaScript using the Fetch API?
- What is CORS, and how do you handle it in JavaScript?
- Explain the difference between the "localStorage" and "sessionStorage" objects.
- How do you manipulate CSS properties in JavaScript?
- What is the "Event" object in JavaScript, and how is it used?
- Describe the difference between "target" and "currentTarget" in event handling.
ES6 and Modern JavaScript Questions
- What are arrow functions in ES6, and how do they differ from regular functions?
- Explain the concept of template literals in ES6.
- What are destructuring assignments in ES6?
- How does the "class" keyword work in ES6 for object-oriented programming?
- What are "promises" in ES6, and how do they differ from callbacks?
- Explain the use of the "async/await" feature in ES6.
- What is the purpose of the "let" and "const" keywords in ES6?
- How can you import and export modules in ES6?
- Describe the "Map" and "Set" data structures in ES6.
- What is the "spread" operator in ES6, and how does it work.
Testing and Debugging Questions
- What are unit tests, and how can you write them in JavaScript?
- Explain the purpose of a test runner in JavaScript testing.
- How can you use the "debugger" statement in JavaScript for debugging?
- Describe the concept of "console.log" and its usage in debugging.
- What is a breakpoint, and how do you set one in a browser's developer tools?
- How can you handle runtime errors in JavaScript code?
- Explain the purpose of "try-catch" blocks in error handling.
- What is linting in JavaScript, and why is it important?
- How do you use the "console.assert" method for debugging?
- What is a stack trace, and how can it help in debugging JavaScript code.
Advanced Topics in JavaScript
- Describe the concept of memoization in JavaScript.
- What is functional programming, and how can it be applied in JavaScript?
- Explain how currying and composition work in functional programming.
- What are Web Workers, and how can they improve JavaScript performance?
- How does lazy loading of scripts enhance web page performance?
- What is the Event Loop and how does it work in JavaScript?
- Describe the purpose of Service Workers in web development.
- How can you achieve immutability in JavaScript objects and arrays?
- What are the differences between "call," "apply," and "bind" in JavaScript?
- Explain the concept of a pure function and its benefits.
- What are WebAssembly and its use cases in JavaScript applications?
- Explain the concept of BigInt and its purpose in JavaScript.
- What are decorators in JavaScript, and how can they be used?
- How does memoization improve the performance of recursive functions?
- What is the Event Emitters pattern, and how can it be used in JavaScript?
- Describe the purpose of the Proxy object and its use cases in JavaScript.
- How does the JavaScript runtime environment differ from the browser environment?
- What is the Event Loop in Node.js, and how does it differ from the browser's Event Loop?
- Explain the concept of microservices and their role in modern web development.
- What are Web Components, and how can they be used in JavaScript applications.
- What is React, and how does it differ from other JavaScript libraries?
- Describe the core concepts of React, such as components, props, and state.
- What is the Virtual DOM in React, and why is it important?
- Explain the concept of "hooks" in React.
- What is Redux, and how does it manage state in a React application?
- What is Angular, and how does it differ from React and Vue?
- Describe the component-based architecture of Angular.
- What is Vue.js, and how does it compare to React and Angular?
- Explain the reactivity system in Vue.js.
- What is the purpose of the "Vuex" library in Vue.js.
Package Managers and Build Tools
- What is npm, and how do you use it in JavaScript development?
- Describe the purpose of package.json in a Node.js project.
- What is Yarn, and how does it differ from npm?
- How do you install and manage third-party libraries using npm or Yarn?
- Explain the role of Webpack in JavaScript development.
- What are Babel and its role in transpiling JavaScript code?
- How does ESLint help maintain code quality in a JavaScript project?
- Describe the purpose of Git and version control in JavaScript development.
- What is Continuous Integration (CI) and how can it be used in JavaScript projects?
- How can you automate tasks in a JavaScript project using tools like Grunt or Gulp.
Security and Best Practices
- What is Cross-Site Scripting (XSS), and how can you prevent it in JavaScript?
- Explain Cross-Origin Resource Sharing (CORS) and its security implications.
- How can you protect against SQL injection in JavaScript?
- Describe the importance of input validation in web applications.
- What are Content Security Policy (CSP) headers and how do they enhance security?
- How can you securely store sensitive information in a JavaScript application?
- Explain the concept of HTTPS and its importance in web security.
- What is the purpose of code splitting, and how can it improve page load times?
- Explain the benefits of lazy loading and how it's implemented in JavaScript applications.
- What is the critical rendering path, and how can you optimize it for better performance?
- Describe the importance of minification and compression in optimizing JavaScript code.
- How does browser caching work, and what are its advantages in web performance?
- What are the best practices for reducing the number of HTTP requests in a web page?
- Explain how the "defer" and "async" attributes in script tags affect page loading.
- How can you profile and optimize JavaScript code using browser developer tools?
- Describe the concept of "Render-Blocking JavaScript" and how to minimize it.
- What are the benefits of using a Content Delivery Network (CDN) for serving JavaScript libraries?
APIs and Asynchronous Programming
- Explain the purpose of the Fetch API for making HTTP requests in JavaScript.
- How do you handle CORS-related issues when making cross-origin requests?
- What is the difference between "GET" and "POST" HTTP methods, and when would you use each?
- Describe the concept of RESTful APIs and their common conventions.
- How can you use the "async" and "await" keywords with the Fetch API for asynchronous operations?
- Explain the purpose of the "XMLHttpRequest" object and its alternatives.
- What is JSON, and how do you parse and stringify JSON data in JavaScript?
- How can you work with asynchronous code using Promises and the "then" method?
- What are WebSockets, and how can they be used for real-time communication in JavaScript?
- Explain the concept of callback hell and how to avoid it in asynchronous code.
- Describe the purpose of the "axios" library for making HTTP requests in JavaScript.
JavaScript Patterns and Best Practices
- What is the Module Pattern, and how does it help organize code in JavaScript?
- Explain the Singleton Pattern and its use in JavaScript applications.
- How does the Observer Pattern work in JavaScript, and when is it useful?
- What is the Revealing Module Pattern, and how does it differ from the Module Pattern?
- Describe the benefits of using the Prototype Pattern in JavaScript.
- How can you implement the Factory Pattern in JavaScript?
- What is the Constructor Pattern, and how is it used to create objects?
- Explain the MVC (Model-View-Controller) pattern and its application in JavaScript frameworks.
- Describe the MVVM (Model-View-ViewModel) pattern and its role in frameworks like Knockout.js.
- How do you implement the Flux architecture in JavaScript applications, and what libraries are associated with it.