JavaScript, explained visually

Learn the language.
See the system.

I'm Lydia Hallie. I write about JavaScript, React, Node, GraphQL, and the ideas underneath them. Every lesson is free, visual, and built to make the confusing parts click.

Start the JavaScript path Open the topic map

21JavaScript lessons

6Big O runtimes

1GraphQL guide

3Field notes

learn.js

// one concept at a time
const learner = {
  name: "you",
  path: "javascript",
  curiosity: Infinity
};

function learn(topic) {
  return `one concept at a time: ${topic}`;
}

learn("closures");

lesson 01 / variables

Choose a path

Six ways into the ecosystem

Start with the language, then follow the thread that fits the problem in front of you.

See every lesson

JavaScript

Learn everything you need to get up and running with JavaScript, from variables and types to closures and the event loop.

21 lessonsStart the path → 02

Data Structures and Algorithms

Learn how to implement sorting algorithms and data structures in JavaScript, and how to reason about their runtimes.

3 tracksOpen the track → 03

GraphQL

Get started with GraphQL and libraries such as Apollo Client and GraphQL Yoga, and see how a schema becomes a query.

1 guideRead the guide → 04

React

Once you have a basic understanding of JavaScript and ES6, the next step is learning how to work with the React library. It lets you create components and manage state in your application.

Related lessonSee the React guide → 05

Node.js

Learning Node.js is a great way to understand the JavaScript language and expand your skills in server side programming. Start with the event loop and the Web APIs that power async code.

Full Stack Projects

Full stack projects can feel daunting when you are starting out. There are certain steps you can take to make the process easier, and the JavaScript path is the foundation for all of them.

FoundationBuild the foundation →

The core path

21 lessons, in the order they click

No dashboards. No certificates. Just a clear sequence that takes you from variables to closures, the call stack, and the event loop.

Each lesson is a short visual walkthrough. Read it in the browser, then try the code in your console. The path is designed to be read in order, but every page stands on its own.

Open the full syllabus Begin with Variables

01 Variables Lesson 02 Primitive Data Types Lesson 03 Operators Lesson 04 Conditionals Lesson 05 Arrays Lesson 06 Array methods and properties Lesson 07 Objects Lesson 08 Functions Lesson

Lesson 01 through 08 of the Complete JavaScript path.

Lydia Hallietheavocoder

Hey! I'm Lydia Hallie, a full stack developer who works with JavaScript, React, Node, GraphQL, and modern web technology every day. I love nothing more than sharing what I know for free and helping more people fall in love with programming.

I also write about TypeScript, GraphQL, web performance, and cloud tools. The through line is simple: make complex ideas easier to see.

Read the longer story

Field notes

Writing beyond the lesson plan

Longer notes on rendering, fonts, and the tools that shape the web.

Browse the notes

GraphQL guide

Learn the language.
See the system.