LESSON 2

How JavaScript Works

Learning objective: Learn where JavaScript runs and how to add it to a page.

Understand

JavaScript runs inside the browser's engine.

You add JavaScript with a <script> tag, ideally just before </body> so the HTML loads first. The browser reads your script top to bottom and runs each statement. Use the developer console to see output and errors.

Analogy: The browser is like a reader following your recipe line by line.

See It in Action

Linking an external script and logging:

<script src="app.js"></script>
<!-- in app.js: -->
console.log("Ready!");
How it works: The <script src> loads your file, and console.log prints a message to the browser console for debugging.

Try It Yourself

  1. Create an app.js file and link it.
  2. Log a message with console.log.
  3. Open dev tools and read the console.

Quick Quiz

Where is it best to place a script tag?

Challenge

Link an external script that logs a message to the console.

Success condition: Your console shows the message from an external script file.