I expect the name `xterm.js` is a reference to `xterm`-the-protocol — being [one of the ANSI X3.64 family mates](https://unix.stackexchange.com/a/5802/138) — as opposed to [`xterm`-the-program](https://invisible-island.net/xterm/), the reference standard for that protocol, maintained by the creator of `vttest`. `xterm`-the-program should score 100% on `vttest`, but I'm not going to bother trying it.