⚡ JavaScript

Make pages interactive. Edit and run every example right here.

1. Getting started with JavaScript
Where JavaScript runs, and your first lines of code.
2. Variables and types
const, let, the basic types, and why === matters.
3. Functions
Function declarations, arrow functions and default values.
4. Arrays and objects
Store data, then transform it with map, filter and reduce.
5. Changing the page
Find elements, react to clicks and update what is shown.
6. Async and fetch
Wait for slow work with promises and async/await.
7. Errors and debugging
Handle failures, and find bugs with the browser tools.
8. JavaScript quick reference
Everyday array, string and object methods on one page.

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