reliable, cross-browser way to get selection's boundaries?

I need to make the user to be able to select some text, click a button and make the server remember the selection for the next time.

I've extensively read through SO's questions and answers, tried some libraries, but without luck: haven't found a reliable tool yet.

It isn't important how the selection's boundaries are identified: it could be "nth textNode, mth char", or "nth char of text", or "nth char of html", or whatever, as long a开发者_JAVA技巧s it allows the server to identify the points in the document; what really matter is that, selecting the same words of the same document must give the same result on chrome, safari, IE, firefox.

EDIT: I don't need it to work everywhere on the internet: just on one site, where the document's structure is fixed and only the content of a single div (or the like) will change.

Try my Rangy library and its Serializer module. I'm not convinced it's exactly what you want because you mentioned the server remembering the selection, whereas my suggestion uses cookies, and the serialized selection will vary between browsers. However, it does do as you described in the first paragraph.

On the other hand, it's pretty much impossible to write something that will work for all browsers and all pages, since browsers interpret HTML differently and build different DOMs.