$().data() return undefined if name contains uppercase

[quaff]

​http://jsfiddle.net/HfuEL/2/

[sindresorhus]

That's because it doesn't find the data-attribute. Data-attributes are automatically lowercased by the browser.

​HTML5 spec:

All attributes on HTML elements in HTML documents get ASCII-lowercased automatically

[quaff]

should jquery auto lowercase and keep correspondence with html5 spec?

[dmethvin]

Nope, if you want mixed case you use the "-" character. Please read these, and followup with a forum post if needed:

​http://www.learningjquery.com/2011/09/using-jquerys-data-apis

​http://api.jquery.com/data/

[[email protected]…]

Would be nice if this was explained as a note in the docs so we know where to start looking.

[dmethvin]

The linked article about data APIs goes into plenty of detail, and says this:

Rule: When accessing data taken from data-* attributes, and especially when accessing the data object directly, use the W3C camelCasing conventions.

In any documentation there will be a tradeoff between describing every detail in every situation on every API where it can arise versus making the documentation readable and comprehensible.