jQuery: get data attribute

Question

In my html I have a span element:

<span class="field" data-fullText="This is a span element">This is a</span>

And I want to get the data-fullText attribute. I tried these two ways, but they didn't work (the both return undefined):

$('.field').hover(function () {
    console.log('using prop(): ' + $(this).prop('data-fullText'));
    console.log('using data(): ' + $(this).data('fullText'));
});

Then I searched and found these questions: How to get the data-id attribute? and jquery can't get data attribute value.
The both's answers are "Use .attr('data-sth') or .data('sth')".
I know that .attr() is deprecated (in jquery-1.11.0, which I use), but, however, I tried it.
And it workded!

Can someone explain why?

Answer 1

You could use the .attr() function:

$(this).attr('data-fullText')

or if you lowercase the attribute name:

data-fulltext="This is a span element"

then you could use the .data() function:

$(this).data('fulltext')

The .data() function expects and works only with lowercase attribute names.