great minds think alike lol

I think the clearest form to use is by far this one

function name(args) {
  // whatever
}

Clearly the current version can be disturbing for a beginner, who may not be able to resolve the kata in one line. This is a 7kyu kata, aimed to complete novices.

It could also be:

const startsWith = (st, prefix) => {
  /* your code here */
}  

If you want to use ES6 style.

Because your code is wrong, it fails with 108 for example. Not a kata issue.