Lesson 1: Your First JavaScript Program - Hello World

What You'll Learn

  • How to create a JavaScript file
  • How to write your first line of code
  • How to run a JavaScript program
  • What console.log() does

Why This Matters

Every programmer starts with a "Hello World" program. It's a simple way to make sure everything works and to see how code turns into output on your screen.

Step 1: Create Your First JavaScript File

  1. Open VS Code and open your node-lessons folder
  2. Create a new folder called lesson-01 in the Explorer panel
  3. Create a new file: Right-click on lesson-01 folder → New File
  4. Name it: hello.js

- The .js extension tells your computer this is a JavaScript file

Step 2: Write Your First Code

Type this into your hello.js file:

console.log("Welcome to programming!");
console.log("My name is [Your Name]");
console.log("I am learning JavaScript");

What Happens When You Run This?

Each console.log() statement prints on a new line:

Welcome to programming!
My name is [Your Name]
I am learning JavaScript

Understanding How Code Runs

When you run a program:

  1. The computer reads your code from top to bottom
  2. It executes each instruction one at a time
  3. The output appears in the terminal

Think of it like following a recipe - you do step 1, then step 2, then step 3, in order.

Step 5: Common Mistakes and How to Fix Them

Mistake 1: Forgetting Quotation Marks

console.log(Hello);  // ❌ ERROR - missing quotes around Hello

console.log("Hello);  // ❌ ERROR - missing closing quote

Fix: Always use matching quotation marks around text:

console.log("Hello");  // ✅ Correct
console.log('Hello');  // ✅ Also correct

Mistake 2: Typos in Keywords

consol.log("Hello!");  // ❌ ERROR - typo in "console"

console.lag("Hello!");  // ❌ ERROR - typo in "log"

Fix: Make sure spelling is exact:

console.log("Hello!");  // ✅ Correct spelling

Exercise 3: Print a Story

Write a program that prints a very short story, one line at a time.

Key Concepts Summary

Concept Definition Example
Statement A single instruction in code console.log("Hi");
String Text data in quotation marks "Hello" or 'Hello'
Function A reusable piece of code that performs an action console.log()
Console The terminal/output area where text appears The black/white text area at bottom of VS Code

What You Learned

  • ✅ How to create a .js JavaScript file
  • ✅ How to use console.log() to print output
  • ✅ How to run JavaScript code with Node.js
  • ✅ How to read error messages and fix simple mistakes
  • ✅ That code runs from top to bottom, line by line

What's Next?

In the next lesson, you'll learn about variables - how to store and reuse information in your programs.