The biggest reason to use JavaScript is that it works in every web browser. There’s nothing to install, so it’s easy to get started and to show your work to other people. And there are basic development tools built into all the major desktop browsers.

Control-Shift-I (or sometimes F12) will bring up the developer tools.

The Elements tab will show you the HTML code for the page, and when you mouse over an element it will highlight it on the page (if it’s on-screen). You can also get here by right-clicking on the page and choosing Inspect (Inspect Element on Firefox).

If you double-click on things in the Elements view you can mess with the text. To the right of the HTML pane there will be a pane with more tabs. If you choose the Styles tab it will show the CSS that applies to the current element. By double-clicking here you can mess with the colors and sizes and such. This won’t get saved anywhere, but it can be fun to experiment with, and is sometimes a good way to debug your layouts and styling.

Anyway. On to JavaScript. If you choose the Console tab at the top of the Developer Tools pane, you’ll get a JavaScript command-line. So if you type alert("AAaaaaaah!"); and hit enter/return, a dialog box will pop up with your message. If you type document.body.append("Blah blah blah"); it will add text onto the end of the page. Though it might show up anywhere, or not at all, since CSS can lay things out in various orders. For instance, on Google’s home page it currently seems to show up at the very top left.

Play with a simple Zdog demo for something a bit more interesting. I haven’t explained the syntax yet, but I’ve tried to make it fairly readable, so see how far you can get just by guessing.