changing data attribute isn't working

Question

I am trying to change a data attribute, but it never seems to get changed and remains as "TEXT", which is the default.

function SuccessGetActorsForGroupCallback(data, el) {
    var str = "";
    jQuery.each(data, function (i, val) {
        str += val + '<br />';
    });

    $(el).data('original-title', str);
    Utilities.ApplyTooltips($(el));
}

Please help

Answer 1

The .data method doesn't alter the data- HTML attribute; it alters a variable that jQuery stores internally.

If you really need/want to alter the data- attribute, do so explicitly with the .attr() method:

$(el).attr('data-original-title', str); 

However, this won't alter the value returned by .data. jQuery will fetch that value from the data- HTML attribute only if it can't find the value stored internally. If you retrieve $(el).data('original-title') again after altering the HTML attribute, you'll find it hasn't changed.

If this is a a problem, use the .removeData() method to delete the internally-stored value. The next time you use .data(), jQuery will see that it's missing and retrieve the data- HTML attribute.

Take a look: http://jsfiddle.net/mblase75/LHCUK/

---

HTML:

<p id="p" data-title="blah"></p>

jQuery:

console.log($('#p').data('title')); // returns "blah"

// alter the attribute directly
$('#p').attr('data-title','whooo'); // data-title="whooo"
// test if .data is changed
console.log($('#p').data('title')); // still returns "blah"

// delete the .data() value
$('#p').removeData('title');
// now fetch it again -- it will retrieve the new data- attribute
console.log($('#p').data('title')); // returns "whooo"

---

Now, in practice, you shouldn't have to worry about this. Just remember that the data- attribute represents the initial value of a .data() variable and not necessarily the current value of that variable, and you'll be fine.

In summary: The .data() method retrieves a value from the HTML element once when the document is loaded, and will not do so again as long as the variable is stored internally.