Phase 0Beginner1 of 16 in JavaScript

Start Here: What JavaScript Is

What JavaScript is, where it runs, how a page loads it, how to use the console, and your first real program. No experience needed.

This phase assumes nothing. You'll learn what JavaScript is, which program actually runs your code (an engine inside the browser or inside Node.js), and why the language is officially called ECMAScript, with a new version every year.

Then you'll put JavaScript on a page the right way (<script>, external files, defer and async), meet the console, the tool you'll use every day to see what your code is doing and read its errors, and write your first program, learning how statements, semicolons, comments and capital letters really work.

Every example is live: edit the code, press Run, and watch both the page and the console. If you haven't met HTML yet, Hectal's /html course starts at the same beginner level; you only need its first phase for this one.

0/4 · 0%

4 topics ~84 min 13 code blocks & diagrams

Start with the first topic

0.1

What JavaScript Is and Where It Runs

JavaScript is the programming language of the web: an engine inside your browser (or inside Node.js on a server) reads your code and runs it, and the language itself is defined by a yearly standard called ECMAScript.

20 min 3 code practice

0.2

Adding JavaScript to a Page

JavaScript reaches a page through the <script> element, either written inline or loaded from a .js file; where you put it and whether you add defer, async or type="module" decides when it runs and what it can see.

19 min 3 code practice

0.3

The Console and DevTools

The console is where your program talks back to you: console.log and its relatives print values, you can type and run JavaScript there directly, and every error shows up with its type, message and the line that caused it.

19 min 3 code practice

0.4

Your First Program

A JavaScript program is a list of statements run from top to bottom; semicolons end statements (and are added automatically in most, but not all, places), comments are notes the engine ignores, and every name is case-sensitive.

26 min 4 code practice

Practise this phase

Hands-on exercises: write the code, see your page live, and press Check to have it tested automatically.

Say hello in the console

Write a program that prints two lines to the console.

Beginner

Fix the capital-letter bugs

This program should print Starting, change the heading to Fixed! and print Done. It has two capital-letter mistakes. Run it, read the errors in the console, and fix them.

Beginner