Word Office Javascript API - Format first x chars

Question

I need to change the size of the first X characters for my add-in. To do this, I should either be able to go through the individual characters or format the first X characters in one go. But I can't find a way to access the individual characters in a Word.Range that works on the web and also on the desktop. So far it only works via the search method. Have I overlooked something?

// slow performance

const charRangeCollection = word.search("*", {
  matchWildcards: true,
  matchCase: false,
  ignoreSpace: true,
  ignorePunct: true,
  matchPrefix: false,
  matchSuffix: false,
  matchWholeWord: false,
});

This does not work with Word under Windows.

const wordChar = wordRange.getRange().split([""]);