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LearnJavaScript

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JavaScript

JavaScript is the only programming language that runs natively in every web browser on the planet. It is also a first-class backend language (Node.js), mobile platform (React Native), and desktop framework (Electron). This track takes you from complete beginner to deep understanding of the V8 engine, concurrency model, and modern ECMAScript features.

200+ Topics

10–14 weeks

5–30 LPA

Start Learning →View Roadmap

Getting Started

Introduction to JavaScript

History, Brendan Eich, Netscape, standardization (ECMAScript), browser + server usage

Setup & Running JS

Browser console, Node.js REPL, VS Code, script tags, type=module

Your First JS Program

console.log, alert, script loading, defer vs async

Language Fundamentals

Variables: var, let, const

Declaration, hoisting, temporal dead zone, block vs function scope

Data Types & typeof

7 primitives, Object, typeof operator, typeof null quirk, dynamic typing

Arithmetic, comparison, logical, bitwise, ternary, nullish coalescing, optional chaining

Implicit vs explicit coercion, == vs ===, truthy/falsy, Abstract Equality Comparison

String methods, template literals, tagged templates, regex basics

IEEE 754 floating point, NaN, Infinity, Number methods, Math object, BigInt

Control Flow

If/Else & Switch

Conditional branching, switch fall-through, break, default

for, while, do-while, for...in, for...of, break, continue, labels

try/catch/finally, throw, Error types, custom errors, error propagation

Functions

Function Basics

Declaration vs expression, anonymous, named, IIFE, arguments object

Arrow Functions

Syntax, lexical this, no arguments object, when to use vs regular functions

Lexical environment, closure creation, practical use cases, module pattern

Higher Order Functions

map, filter, reduce, forEach, find, some, every, flatMap

Rest parameters, spread in calls/arrays/objects, shallow copy

Array destructuring, object destructuring, default values, aliasing, nested

Generators & Iterators

function*, yield, iterator protocol, Symbol.iterator, infinite sequences

Currying & Partial Application

Currying technique, partial application, compose, pipe functions

Objects & Prototypes

Object literal, property access, dynamic keys, computed properties, shorthand

Prototypal Inheritance

prototype chain, __proto__, Object.create, Object.getPrototypeOf

class syntax, constructor, methods, static, private fields (#), inheritance, super

this in global, object, class, arrow function, event handlers, explicit binding

Object.keys/values/entries, assign, freeze, seal, create, defineProperty

Arrays

Arrays Fundamentals

Creation, indexing, length, sparse arrays, holes, Array.from, Array.of

Array Methods Deep Dive

push, pop, shift, unshift, splice, slice, concat, flat, flatMap, at, findIndex

Array Iteration Methods

forEach, map, filter, reduce, reduceRight, find, findIndex, some, every

sort stability, comparison function, locale compare, sort complex objects

Asynchronous JavaScript

Call stack, Web APIs, Task queue, Microtask queue, rendering pipeline, V8 internals

Microtasks & Macrotasks Deep Dive

Call Stack, Microtask Queue (Promises), Macrotask Queue (setTimeout), rendering order

Callback pattern, callback hell, error-first callbacks, Node.js conventions

Promise states, then/catch/finally, chaining, Promise.all/race/allSettled/any

async functions, await expression, error handling, parallel vs sequential, top-level await

GET/POST/PUT/DELETE requests, headers, JSON, error handling, AbortController

setTimeout, setInterval, clearTimeout, clearInterval, requestAnimationFrame, queueMicrotask

DOM & Browser APIs

Document, nodes, elements, text nodes, querySelector, getElementById, DOM tree

DOM Manipulation

createElement, appendChild, innerHTML, textContent, classList, setAttribute

addEventListener, event object, bubbling, capturing, delegation, preventDefault, stopPropagation

localStorage, sessionStorage, IndexedDB, cookies comparison

Intersection & Mutation Observers

IntersectionObserver for lazy loading, MutationObserver for DOM changes

Modern JavaScript (ES6–ES2024)

import/export, named vs default, dynamic import(), module bundlers overview

Symbol & Well-Known Symbols

Symbol creation, Symbol.iterator, Symbol.toPrimitive, use cases

Proxy & Reflect

get/set/has traps, Reflect API, reactive systems, validation proxies

WeakMap, WeakSet & WeakRef

Weak references, memory management, private data pattern, WeakRef

ES2022–ES2024 Features

at(), hasOwn, private class fields, error cause, Array.fromAsync, groupBy

V8 & Performance

V8 Engine Internals

Ignition interpreter, TurboFan compiler, hidden classes, inline caches, JIT compilation

Memory Management & GC

V8 heap, garbage collection, generational GC, memory leaks, DevTools memory profiling

Performance Best Practices

Avoiding layout thrashing, debounce/throttle, memoization, Web Workers

Web Workers & SharedArrayBuffer

Background threads, postMessage, Atomics, SharedArrayBuffer, structured cloning

Interview Preparation

Beginner Interview Questions

Top 50 JS basics for freshers and frontend interviews

Advanced Interview Questions

Closures, this, event loop, prototype, hoisting — senior engineer level

JavaScript MCQs

300+ MCQs for placement preparation

JavaScript Cheatsheet

Quick reference card for syntax, methods, async patterns

Companies Using JavaScript

GoogleMetaNetflixAirbnbShopifyLinkedInInfosysWiproTCS