Any application that can be written in JavaScript will eventually be written in JavaScript.
Atwood proposed it in 2007 as a corollary to Berners-Lee's rule of least power. Desktop applications, mobile apps and spreadsheets have since largely confirmed it.
In practice
- A team builds an internal desktop tool in Electron because the three people available write JavaScript.
- A hardware startup ships its configuration utility as a web page because that is what its web team could build.