What I had in mind was Unicode string normalization, comparison and sorting as well as finding the length of strings correctly when they contain combining characters, ligatures and such. What is the library of choice for this?

For anyone curious about the potential issues there is a good article about the flaws in JavaScript's handling of Unicode at http://mathiasbynens.be/notes/javascript-unicode#accounting-.... HN discussion: https://news.ycombinator.com/item?id=7221362.