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Understanding arrays in javascript

Promises represent eventual completion or failure of async operations with three states (pending, fulfilled, rejected), and async/await provides syntactic sugar for writing promise-based code that reads like synchronous code.

A closure is a function that retains access to variables from its outer (enclosing) scope even after the outer function has returned, enabled by JavaScript's lexical scoping.

A Single Page Application loads one HTML document and uses JavaScript to dynamically rewrite content and manage navigation via the History API, avoiding full page reloads.

ES6 introduced Map and Set as specialized alternatives to plain objects and arrays — Map allows any key type with guaranteed order, while Set stores unique values with O(1) lookups.

JavaScript has 7 primitive types (string, number, bigint, boolean, undefined, null, symbol) that are immutable and passed by value, plus Object as the non-primitive reference type.

Destructuring extracts values from arrays (by position) and objects (by property name) into variables. The spread operator (...) expands iterables, while the rest operator (...) collects remaining elements.

The Document Object Model (DOM) is a tree-structured programming interface that lets JavaScript read, modify, and respond to a web page's content, structure, and styles in real time.

JavaScript provides try/catch/finally for synchronous error handling and .catch() or try/catch with async/await for asynchronous errors, with built-in error types like TypeError, ReferenceError, and SyntaxError.

DOM events flow through three phases — capture, target, and bubble — and event delegation leverages bubbling to handle events on dynamic child elements with a single parent listener.

Arrow functions lexically bind 'this' from their enclosing scope and have concise syntax, while regular functions dynamically bind 'this' based on how they're called and can be used as constructors.

Generators are functions that can pause and resume execution using yield, producing values on demand. They implement the iterator protocol, enabling lazy evaluation, infinite sequences, and custom iteration with for...of.