JavaScript: The Complete Language

How JavaScript runs in the browser and Node.js

JavaScript engine, V8, call stack, runtime environment, browser vs Node.js, script execution, console

var vs let vs const - which one to use and when

var hoisting, let block scope, const immutability, temporal dead zone, variable declaration best practices, re-assignment vs re-declaration

JavaScript data types explained with typeof

primitive types, string, number, boolean, null, undefined, symbol, bigint, typeof operator, dynamic typing, type coercion basics

JavaScript operators and operator precedence

arithmetic operators, comparison operators, logical operators, nullish coalescing, optional chaining, ternary operator, short-circuit evaluation, operator precedence

Control flow: if, else, switch, and loops in JavaScript

if-else, switch statement, for loop, while loop, do-while, for-of, for-in, break, continue, truthy and falsy values

Function declarations vs function expressions vs arrow functions

function declaration, function expression, arrow function, hoisting of functions, anonymous functions, named function expressions, syntax differences

Scope chain and lexical scope in JavaScript

global scope, local scope, block scope, scope chain, lexical scope, variable shadowing, scope lookup order, nested functions

Closures in JavaScript explained with real examples

closure definition, persistent scope, factory functions, private variables, closure in loops, practical use cases, memory implications

Default parameters, rest parameters, and the spread operator

default parameters, rest parameters, spread operator, arguments object vs rest, spreading arrays, spreading objects, function arity, parameter destructuring

Higher-order functions: map, filter, reduce explained

higher-order functions, first-class functions, Array.map, Array.filter, Array.reduce, callback functions, method chaining, functional programming basics

JavaScript objects: creating, accessing, and mutating

object literals, dot notation, bracket notation, computed property names, property shorthand, Object.keys Object.values Object.entries, property existence check, delete operator

Arrays: methods every JavaScript developer must know

push pop shift unshift, splice slice, indexOf includes find findIndex, sort, flat flatMap, Array.from Array.isArray, forEach vs map differences, mutation vs immutability

Destructuring arrays and objects in JavaScript

array destructuring, object destructuring, default values in destructuring, renaming variables, nested destructuring, function parameter destructuring, swap pattern

Prototypes and prototype chain in JavaScript

prototype chain, Object.prototype, __proto__, Object.create, prototype-based inheritance, hasOwnProperty, prototype vs class, property lookup order

ES6 classes in JavaScript: syntax, inheritance, and pitfalls

class declaration, constructor, instance methods, static methods, inheritance with extends, super keyword, private fields, class fields, instanceof

The JavaScript event loop explained simply

event loop, call stack, web APIs, callback queue, microtask queue, task queue, setTimeout behavior, synchronous vs asynchronous, non-blocking I/O

Promises in JavaScript: how to create and consume them

Promise constructor, resolve reject, then catch finally, Promise states, chaining promises, error propagation, Promise.resolve Promise.reject, returning from then

async/await: writing asynchronous code that reads synchronously

async function, await keyword, try-catch with async-await, returning from async functions, async functions return promises, parallel execution, error handling patterns

Promise.all, Promise.race, Promise.allSettled, Promise.any explained

Promise.all, Promise.race, Promise.allSettled, Promise.any, AggregateError, concurrent async patterns, timeout pattern, error handling differences

Fetching data from APIs with fetch and handling errors

fetch API, Request Response objects, response.json, HTTP status codes, network errors vs HTTP errors, AbortController, headers, POST request, error handling pattern

Selecting and modifying DOM elements with JavaScript

querySelector, querySelectorAll, getElementById, innerHTML vs textContent, createElement, appendChild, insertAdjacentHTML, removeElement, classList, dataset attributes

JavaScript event listeners: handling user interaction

addEventListener, removeEventListener, event object, event.target vs event.currentTarget, event propagation, bubbling, capturing, stopPropagation, preventDefault, event delegation

Local Storage and Session Storage in JavaScript

localStorage API, sessionStorage API, setItem getItem removeItem clear, JSON serialization, storage limits, storage events, when to use each, security considerations

The Intersection Observer and Mutation Observer APIs

IntersectionObserver, threshold, rootMargin, lazy loading pattern, MutationObserver, observing DOM changes, childList subtree, disconnecting observers, performance vs event listeners

Timers, requestAnimationFrame, and browser rendering performance

setTimeout, setInterval, clearTimeout clearInterval, requestAnimationFrame, requestIdleCallback, animation loop pattern, layout thrashing, will-change, performance.now

ES modules: import and export syntax in JavaScript

named exports, default export, import syntax, re-exporting, dynamic import, module scope, circular dependencies, tree shaking, import.meta

Error handling in JavaScript: try-catch, custom errors, and error types

try-catch-finally, Error types, ReferenceError TypeError SyntaxError, custom error classes, error.message error.stack, rethrowing errors, error boundaries pattern, handling async errors

Iterators and generators in JavaScript explained

iterator protocol, Symbol.iterator, custom iterables, generator functions, yield keyword, Generator object, infinite sequences, generator-based async, lazy evaluation

Proxy and Reflect: intercepting JavaScript object operations

Proxy constructor, handler traps, get set has deleteProperty, Reflect API, use cases validation reactivity logging, Proxy vs Object.defineProperty, revocable proxies

WeakMap, WeakSet, and memory management in JavaScript

WeakMap, WeakSet, garbage collection, strong vs weak references, use cases private data caching, Map vs WeakMap differences, memory leaks patterns, FinalizationRegistry