For a long time React docs had a very prominent place for "React without JSX" that showed that JSX was nothing but a bunch of functions [1], and you could skip all of them by doing

  var h = React.createElement

  h(...)

A few people where doing that. And early on you could switch to Preact by substituting Preact.* functions for React.* functions in the transpilation tools.

[1] It's still there in advanced guides: https://reactjs.org/docs/react-without-jsx.html