New to JavaScript? This is the reference section — dip in to any topic.
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🌱 Beginner Foundation
Everything you need to go from zero to writing real JavaScript programs. Start here if you're new.
What is JavaScript
What JS is, where it runs, how it relates to HTML/CSS. The two homes: browser and Node.js.
Setup & Running
Browser console, script tags, Node.js install, the REPL. Running your first program.
Syntax & Statements
Semicolons, comments, blocks, ASI — the grammar rules JavaScript uses to read your code.
Variables — let, const, var
Storing information. Why const is the default, when to use let, why var is legacy.
Data Types
The 7 primitives, typeof, null vs undefined — the type system explained plainly.
Numbers & Math
One number type, NaN, Infinity, the Math object, BigInt.
Strings
String literals, template literals (the JS f-string), methods, immutability.
Booleans & Comparison
true/false, == vs ===, the falsy list — the most important JS beginner lesson.
Type Coercion & Casting
Implicit coercion, Number(), String(), Boolean() — where JS surprises live.
Control Flow
if/else, switch, for, while, for...of, for...in — making decisions and repeating things.
Arrays
The workhorse data structure — create, access, add/remove, loop, spread, destructuring.
Objects
Key-value pairs, dot vs bracket access, methods, Object.keys/values/entries, JSON.
Functions
Declarations vs expressions, arrow functions, default params, first-class functions.
Scope & Closures
Block scope, the closure concept, the classic loop trap — gateway to async.
User Input & Output
console.log, prompt/alert in browser, readline in Node — two homes, explained honestly.
Error Handling
try/catch/finally, Error types, throwing custom errors — understanding the console.
⚙️ Core Language
Deeper JavaScript — the features that power real applications. Requires the beginner foundation above.
OOP & Classes
class, constructor, extends, super, static — ES6+ class syntax demystified.
Async & Promises
callbacks → Promises → async/await → fetch. The event loop explained.
DOM & Events
querySelector, addEventListener, classList — making web pages interactive.
Modules (ESM)
import/export, named vs default, ESM vs CommonJS — how JS organises large codebases.
Iterators & Generators Coming soon
The iteration protocol, Symbol.iterator, generator functions, yield.
Destructuring & Spread Coming soon
Array and object destructuring, the spread operator, rest params — modern JS patterns.
🌐 Ecosystems
JavaScript's major environments and frameworks — each is a world of its own.
Node.js Coming soon
Server-side JS. fs, http, path, process — building backends without a browser.
Express.js Coming soon
The most-used Node.js web framework. Routes, middleware, REST APIs.
React Coming soon
Component-based UIs. JSX, hooks, state, props — the most-used frontend library.
Next.js Coming soon
Full-stack React. SSR, SSG, App Router, API routes — deploy to Vercel.
🐍 Coming from Python?
JavaScript and Python share the same ideas (variables, loops, functions, objects) but
express them differently. The biggest adjustments: JS uses { } instead of
indentation, has two keyword families for variables (let/const), and
runs asynchronously by default. Each page in this reference flags Python differences
where they matter most.