I want to change styles with JavaScript, but I would prefer that the styles be written in CSS in a style sheet for organization reasons. I know I can invoke an alternate stylesheet with JS:
<link rel="alternate stylesheet" type="text/css" title="big-style"
but there might be many of these alternatives and I'd prefer all CSS was in a single file (for performance). Just as you can have many blocks of styles (in same file) activated by media queries, I'd like to have in a single file many blocks of styles that can be triggered by JavaScript.

Is this possible?