> ## Documentation Index
> Fetch the complete documentation index at: https://js.maxbraglia.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Running JavaScript

> Different ways to run JavaScript code during development

## Three ways to run JavaScript

You'll use three environments during this course. Each one is useful for different things.

## Node.js in the terminal

Run any `.js` file from your terminal:

```bash theme={null}
node myfile.js
```

This is what you'll use for most of the learning sections (JavaScript Core, Working with Data, Async & APIs). It's the closest thing to running `python myfile.py`.

```javascript practice.js theme={null}
const prices = [29.99, 49.99, 9.99, 79.99];
const total = prices.reduce((sum, price) => sum + price, 0);
console.log(`Total: $${total.toFixed(2)}`); // "Total: $169.96"
```

```bash theme={null}
node practice.js
# Total: $169.96
```

<Tip>
  Create a `practice.js` file in your `js-practice` folder. Use it as a scratch pad — edit it, run it, edit it again. You don't need a new file for every experiment.
</Tip>

## Browser console

Open any browser, press `F12`, and use the Console tab for quick experiments.

```javascript theme={null}
// Good for: testing one-liners, checking syntax, quick math
"hello".toUpperCase()  // "HELLO"
[1, 2, 3].includes(2)  // true
typeof null  // "object" (yes, really)
```

The browser console is interactive — it evaluates each line and shows the result. No `console.log()` needed for simple expressions.

<Warning>
  The browser console has access to web APIs (like `document` and `window`) that Node.js doesn't have. If you're testing pure JavaScript logic, either environment works. If you're testing DOM or browser features, use the browser console.
</Warning>

## VS Code integrated terminal

The integrated terminal in VS Code (`` Ctrl+` ``) runs Node.js commands without leaving your editor. This is where you'll spend most of your time:

1. Write code in the editor panel
2. Switch to the terminal (`` Ctrl+` ``)
3. Run `node filename.js`
4. See the output
5. Edit and repeat

```bash theme={null}
# Your typical workflow:
node hello.js
# (see output, make changes, run again)
node hello.js
```

<Info>
  Later in the course, when you work with React, you'll run `npm run dev` in this terminal to start a development server. The server watches for file changes and refreshes your browser automatically.
</Info>

## Which one should I use?

| Environment                  | Best for                                                |
| ---------------------------- | ------------------------------------------------------- |
| **Node.js** (`node file.js`) | Writing and running JavaScript files, course exercises  |
| **Browser console** (`F12`)  | Quick experiments, testing one-liners, DOM/browser APIs |
| **VS Code terminal**         | Everything — it runs Node.js from within your editor    |

For this course, you'll mostly use VS Code's integrated terminal to run Node.js. The browser console is there for quick checks.

## What's next?

You can write and run JavaScript. Before we dive into the language itself, let's understand npm — the tool that manages JavaScript packages and dependencies.

<Card title="Understanding npm" icon="cube" href="/getting-started/understanding-npm">
  How JavaScript manages packages and dependencies
</Card>