HTML transformations

You may want to make universal changes to the HTML of your books just before they are output. These are called transformations.

The template already includes some transformations:

• For accessibility purposes, the epubAriaSidenotes transformation gives all elements with the class sidenote the ARIA attribute role="note".
• We use transformations in PDF to generate QR codes from include qr-code tags.

Transformations are currently supported for epub and EPUB outputs only.

To add a transformation for epub output, add a file containing a single function file to _tools/gulp/transformations/epub. You would do the same for PDF by adding a function file to _tools/gulp/transformations/pdf.

For guidance on the structure of the function, follow the existing files. For syntax, these functions use Cheerio.