JavaScript J09 lab

From the extracted companion folder, open javascript/j09/index.html.
Use the local server below; double-clicking is not the supported run path.

Server: open a terminal in the extracted companion/javascript folder.
Run: python -m http.server 8000 --bind 127.0.0.1
Windows alternative: py -m http.server 8000 --bind 127.0.0.1
Leave that terminal running, then visit http://127.0.0.1:8000/j09/
Stop the server with Ctrl+C when finished.

Logic tests: Node 22 or newer. Check node --version first.
From companion/javascript run: node --test j09/tests.mjs
No npm install is needed. Tests do not replace browser interaction checks.

Read the matching J09 book lesson for predictions and deliberate mistakes.
Exercise solutions: javascript/solutions/J09.md
All data are fictional; no live analytics service or credentials are used.
