Q771. How does the Mutation Observer API work?
The MutationObserver API provides a way to watch for changes to the DOM tree, replacing the deprecated mutation events. **Basic usage:** ```javascript const observer = ne...
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Q772. What is tail call optimization and does JavaScript support it?
Tail call optimization (TCO) is a technique where a function call in tail position (the last operation before returning) reuses the current stack frame instead of creatin...
Q773. What are the different ways to handle circular references in JSON?
Circular references occur when an object references itself directly or indirectly, causing `JSON.stringify()` to throw an error. **Problem:** ```javascript const obj = { ...
Q774. How do you implement a singleton pattern in JavaScript?
The singleton pattern ensures a class has only one instance and provides a global access point to it. **Classic singleton with closure:** ```javascript const Singleton = ...
Q775. What is the Performance API and how is it used for measuring performance?
The Performance API provides high-precision timing information for measuring web application performance. **Basic timing:** ```javascript // High-resolution timestamp con...
Q776. What are the differences between SharedArrayBuffer and ArrayBuffer?
SharedArrayBuffer and ArrayBuffer are both fixed-length binary data buffers, but SharedArrayBuffer allows sharing memory between multiple workers/threads. **ArrayBuffer (...
Q777. How do you prevent prototype pollution attacks in JavaScript?
Prototype pollution is a security vulnerability where attackers inject properties into Object.prototype, affecting all objects in the application. **Vulnerable code:** ``...
Q778. What is the Atomics API and when should it be used?
The Atomics API provides atomic operations on SharedArrayBuffer, ensuring thread-safe access to shared memory in multi-threaded JavaScript (workers). **Basic atomic opera...
Q779. How do you implement a lazy loading pattern for modules?
Lazy loading defers module loading until they're actually needed, reducing initial bundle size and improving load time. **Dynamic import (ES modules):** ```javascript // ...
Q780. What are the best practices for optimizing JavaScript bundle size?
Optimizing bundle size improves load times, reduces bandwidth usage, and enhances user experience, especially on slow networks. **1. Code splitting:** ```javascript // Sp...