PostHTMLExtendAttrs is plugin for PostHTML. It extend HTML attrs with new attrs and data.
var posthtml = require('posthtml'),
html = '<div class="wow">OMG</div>';
posthtml([ require('posthtml-extend-attrs')({
attrsTree: { '.wow' : { id: 'wow_id' }}
})])
.process(html)
.then(function(result) {
console.log(result);
});
// <div class="wow" id="wow_id">OMG</div>