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JavaScript Interview Questions - 2025 Edition

🔥 Core JavaScript Fundamentals​

  1. JavaScript Definition & Runtime Environment
  2. JavaScript Engine (V8, SpiderMonkey, JavaScriptCore)
  3. Execution Context & Call Stack
  4. Hoisting (var, let, const, functions)
  5. Scope & Scope Chain (Global, Function, Block)
  6. Closures & Lexical Scoping
  7. Temporal Dead Zone (TDZ)
  8. Variable Declarations: var vs let vs const

🚀 Functions & Advanced Concepts​

  1. Function Declaration vs Function Expression vs Arrow Functions
  2. Higher-Order Functions
  3. Function Methods: call(), apply(), bind()
  4. Currying & Partial Application
  5. Function Composition
  6. IIFE (Immediately Invoked Function Expression)
  7. Default Parameters & Rest/Spread Operators
  8. Generator Functions & Iterators

🎯 Objects & Prototypes​

  1. Prototypal Inheritance
  2. Prototype Chain
  3. proto vs prototype property
  4. Object.create() & Object.setPrototypeOf()
  5. Constructor Functions vs Classes
  6. Object Methods: freeze(), seal(), keys(), values(), entries()
  7. Object Destructuring & Property Shorthand
  8. Getters & Setters
  9. Private Fields & Methods (ES2022)

📚 Arrays & Data Structures​

  1. Array Methods: map(), filter(), reduce(), find(), forEach(), some(), every()
  2. Array Sorting (numbers, strings, objects)
  3. Array Flattening (flat(), flatMap())
  4. Set & WeakSet
  5. Map & WeakMap
  6. Symbol & Symbol.iterator
  7. Typed Arrays (Int8Array, Float32Array, etc.)

⚡ Asynchronous JavaScript​

  1. Event Loop, Call Stack, Callback Queue
  2. Microtasks vs Macrotasks
  3. Callbacks & Callback Hell
  4. Promises (then, catch, finally)
  5. Promise.all(), Promise.race(), Promise.allSettled(), Promise.any()
  6. Async/Await
  7. Error Handling in Async Code
  8. AbortController & AbortSignal

🌐 Modern JavaScript (ES6+)​

  1. Template Literals & Tagged Templates
  2. Destructuring (Arrays & Objects)
  3. Modules (import/export, dynamic imports)
  4. Optional Chaining (?.) & Nullish Coalescing (??)
  5. Logical Assignment Operators (&&=, ||=, ??=)
  6. BigInt & Number methods
  7. String Methods: includes(), startsWith(), endsWith(), padStart(), padEnd()
  8. Array.from() & Array.of()

🎨 DOM & Browser APIs​

  1. Event Handling & Event Object
  2. Event Bubbling & Event Capturing
  3. Event Delegation
  4. preventDefault() & stopPropagation()
  5. Custom Events
  6. Intersection Observer API
  7. Mutation Observer API
  8. Web Workers & Service Workers
  9. Local Storage, Session Storage, IndexedDB

⚙️ Performance & Optimization​

  1. Debouncing & Throttling
  2. Memoization
  3. Lazy Loading & Code Splitting
  4. Memory Management & Garbage Collection
  5. Performance Monitoring (Performance API)
  6. Web Vitals (CLS, FID, LCP)
  7. Tree Shaking & Bundle Optimization

🔧 Advanced Topics​

  1. this Keyword (Context Binding)
  2. Proxy & Reflect API
  3. WeakRef & FinalizationRegistry
  4. Atomics & SharedArrayBuffer
  5. Regular Expressions (RegExp)
  6. Error Types & Custom Errors
  7. JSON Methods & Serialization
  8. Strict Mode

🏗️ Design Patterns​

  1. Module Pattern & Revealing Module Pattern
  2. Singleton Pattern
  3. Factory Pattern
  4. Observer Pattern (Pub/Sub)
  5. Command Pattern
  6. Decorator Pattern
  7. Proxy Pattern
  8. Strategy Pattern
  9. Builder Pattern
  10. Adapter Pattern

💻 Coding Challenges​

  1. String Manipulation (Reverse, Palindrome, Anagram)
  2. Array Problems (Two Sum, Find Duplicates, Intersection/Union)
  3. Object Deep Clone & Comparison
  4. Implement Array Methods (map, filter, reduce)
  5. Implement Promise & Promise.all()
  6. Implement Debounce & Throttle
  7. Flatten Nested Arrays/Objects
  8. LRU Cache Implementation

🔒 Security & Best Practices​

  1. XSS Prevention
  2. CSRF Protection
  3. Content Security Policy (CSP)
  4. Same-Origin Policy & CORS
  5. Input Validation & Sanitization
  6. Secure Coding Practices

🌟 2025 Trending Topics​

  1. Web Components & Custom Elements
  2. Progressive Web Apps (PWA)
  3. WebAssembly (WASM) Integration
  4. Server-Side Rendering (SSR) Concepts
  5. Micro-frontends Architecture
  6. Edge Computing & Edge Functions
  7. AI/ML Integration in JavaScript
  8. WebRTC & Real-time Communication
  9. Blockchain & Web3 JavaScript APIs

📖 Essential Resources​