In the README.md you state that jQuerys .data() method renders your plugin redundant. This is not the case as .data() will not access the data-attribute. Instead, jQuery has an internal data store that holds the "data" assigned to each DOM element.

For convenience jQuery will initially fill that data store with the values of the data-attributes when you first select it using jQuery.

That means, that you can't change the value of the data-attribute using .data(). You also will not receive any changes to the data attributes value using .data().

Example:

<div id="test" data-hello="world"></div>

var $test = $('#test');

// You can get the value of the data attribute using .data() after the element has
// been selected for the first time:
$test.data('hello');      //=> 'world'
$test.attr('data-hello'); //=> 'world'

Now lets change the data using .data():

// When you change the data using .data(), the attribute value won't change:
$test.data('hello', 'data');
$test.data('hello');      //=> 'data'
$test.attr('data-hello'); //=> 'world'

<div id="test" data-hello="world"></div>

As you can see, the attribute value has not changed. Now lets use .attr() to update the value of our data-attribute:

// Vice versa, changing the attribute value will not update the data value:
$test.attr('data-hello', 'attribute');
$test.data('hello');      //=> 'data'
$test.attr('data-hello'): //=> 'attribute'

<div id="test" data-hello="attribute"></div>

Now the attribute value has changed but .data() still returns 'data' rather than 'attribute'.

This is essential when you want to use the data-attribute with CSS:

<div id="my-elem" data-size="small">
    <!-- ... -->
</div>

[data-size="small"] {
    /* ... */
}

[data-size="large"] {
    /* ... */
}

$('#my-button').on('click', function() {
    var $myElem = $('#my-elem');

    $myElem.data('size', 'large');      // This will have no effect.
    $myElem.attr('data-size', 'large'): // Yep, that works.
    $myElem.dataAttr('size', 'large');  // Like a charm!
});

you know the drill