JavaScript

Variables

Store values with let and const, and print them with console.log.

7 minFree preview

Data types

Numbers, strings, booleans and friends, plus how to check what type a value is.

7 minFree preview

Making decisions with if

Run different code depending on a condition using if, else and comparison operators.

7 min Account

Loops

Repeat code with for and while loops instead of copying and pasting.

7 min Account

Functions

Wrap code in a named, reusable function with parameters and a return value.

8 min Account

Arrays

Lists of values, and the methods that add, remove, search and transform them.

9 min Account

Objects

Group related data with key-value pairs, read and change properties, and loop over them.

8 min Account

The DOM

Select elements on a page and change their text, style and structure with JavaScript.

9 min Account

Events

React to clicks, key presses and form input with addEventListener.

8 min Account

Async and await

Write code that waits for slow things without freezing the page, using promises and async functions.

9 min Account

Fetch and APIs

Get data from a server with fetch, read JSON, and handle errors and loading states.

9 min Account

Modern ES6+ features

Destructuring, spread, template strings, default parameters, optional chaining and more.

9 min Account

Error handling

try, catch, finally and throw: handle problems without crashing, and raise your own errors.

8 min Account