Unit 3 of 3 · Intermediate · 61 min total

Scripting & Storage. Where pages become software.

Seven lessons that take you from JavaScript fundamentals through DOM manipulation, talking to APIs, server-side code, databases, and the security mistakes you can’t afford to ship.

JavaScript basics

9 min read

Variables (let, const, var), the eight types, arrays, functions, and where JS actually runs. Plus the loose-typing footguns and how to dodge them.

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The DOM & events

9 min read

How the browser turns HTML into an object tree, how to query and mutate it, and the event listeners that make pages interactive — click, submit, keydown, the works.

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Async, fetch & APIs

9 min read

Why JavaScript is single-threaded but does async, promises and async/await in plain English, fetch(), and what an HTTP API actually feels like to call.

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Client vs server-side code

8 min read

Where code runs and why it matters. Server-side rendering, client-side rendering, PHP and Node and serverless functions. Why secrets never go in client code.

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Cookies, sessions & storage

8 min read

Cookies, sessions, localStorage, sessionStorage, and IndexedDB. What to put where, what survives a refresh, and the privacy and security tradeoffs.

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Database basics

9 min read

Relational vs document, SQL CRUD in one example, the three queries you'll write 95% of the time, and how ORMs (Prisma, Drizzle) fit on top.

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Web security 101

9 min read

XSS, SQL injection, CSRF, broken auth, and the OWASP top hits. The mistakes that turn a working app into a breach, and the patterns that prevent them.

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When you finish the lessons

Test what stuck. 20 questions, 5 minutes.

You’ll get a score and a per-topic breakdown across JavaScript, the DOM, async, databases, and security. If you crush this one, you’re ready to ship.

Take the JS & Storage Quiz →

When the quiz feels easy

Go build something — and don’t ask permission.

You’ll know enough at the end of this to ship a real web app: a static front-end, a JS client, an API, a database, and the security to not get owned. The next move is not another tutorial. Pick a thing. Build it. Ship it.

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