Is there a mechanism for generating a book index if there is the follwing markup in the html document?

<span class="role-index-term" id="__IDX1__"><span class="role-index-term-1">Sample Mainentry</span><span class="role-index-term-2">Sample Subentry</span></span>

It will require writing JavaScript to scan for these terms and add links to them from the index section.