a 要素 headers 属性 (HTML)

[1] ericelliott/jiron: Make your API self documenting and your clients adaptable to API changes. ( (2017-01-30 00:06:17 +09:00)) <https://github.com/ericelliott/jiron#support-for-headers-in-links>

Support for headers in links:
a(headers='Accept:application/vnd.jiron+jade') Some Jiron resource
Which would translate to this, if HTML knew how to deal with it:
<a headers="Accept:application/vnd.jiron+jade">Some Jiron resource</a>
The Jiron client will attach a link activation handler that will set the appropriate accept header and fetch the resource using AJAX.