So it all depends on the developer how they want to access the data. You might want to take a look at https://github.com/GCheung55/mootools-htmlx/blob/master/Source/Elements/Elements.Dataset.js
It provides a getData, setData, getDataset, and eraseData methods. It also goes along with the W3 spec for data attributes and dataset. So you can set them either hyphenated or camelCased.
