javascript

JavaScript uses prototypal inheritance where objects inherit directly from other objects through a prototype chain. Each object has an internal [[Prototype]] link that forms a chain used for property lookup until null is reached.

Generators are functions that can pause execution and resume later, yielding multiple values over time. They're defined with function* syntax and return an iterator. Use cases include lazy evaluation, infinite sequences, and custom iterables.

A Proxy wraps an object and intercepts fundamental operations (get, set, delete, etc.) through handler traps. They enable metaprogramming patterns like validation, logging, lazy loading, and implementing reactive systems.

JavaScript uses automatic garbage collection with a mark-and-sweep algorithm. Objects are collected when unreachable from roots (global, stack). Memory leaks occur from uncleared references like closures, event listeners, intervals, and DOM references.

The Module pattern encapsulates code using closures to create private state. ES6 modules are the standard with static imports (analyzed at compile time), while CommonJS uses dynamic require() at runtime. ES6 supports tree-shaking and async loading.

CORS (Cross-Origin Resource Sharing) is a browser security mechanism that blocks cross-origin requests unless the server explicitly allows them via HTTP headers like Access-Control-Allow-Origin.