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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

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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...

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