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JavaScript Fundamentals

Level
11 lessons74 exercises~20h

74 hands-on exercises to learn JavaScript from scratch. Variables, math, arrays, objects, classes, DOM manipulation, async programming and REST APIs, all runnable in your browser.

01. Variables & Basics

Variables, alerts, prompts and conditionals.

What you will learn

Every JavaScript program starts with variables: named containers that store values. In this lesson you will declare variables, interact with the user through alert() and prompt(), and make decisions with if / else.

Key concepts

  • let and const: block-scoped variable declarations
  • alert(): display a message to the user
  • prompt(): ask the user for input (returns a string)
  • confirm(): ask a yes/no question (returns a boolean)
  • if / else if / else: conditional execution

Resources

📖 MDN: let 📖 MDN: const 📖 MDN: Conditionals 📝 JavaScript.info: Variables

Exercises (4)

Variables & Alert

●●●

Create a variable with the name of your choice and set its value to the string "Hello, World!". Display it using console.log().

JavaScript
Output
Click "Run" to execute your code...

Frequently Asked Questions

Do I need prior programming experience to take this course?

No. The course starts from absolute zero (declaring variables, basic math, and string operations) and builds up progressively to advanced topics like async/await and REST APIs. Basic HTML knowledge is helpful but not strictly required.

Can I run the exercises without installing anything?

Yes. Every exercise runs directly in your browser using the built-in CodePlayground. There is nothing to install: no Node.js, no editor, no terminal. Just open the lesson and start coding.

How long does it take to complete all 74 exercises?

The estimated time is around 20 hours at a comfortable pace. Each lesson has between 3 and 14 exercises of increasing difficulty. You can work through them at your own speed and revisit any exercise at any time.

Is this course really free?

Yes, completely free: no sign-up, no paywall, no ads, no tracking. CodeHelper is an open educational resource supported by the community.

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