I've got the following field on an MVC view:
@Html.TextBoxFor(model => model.Course.Title, new { data_helptext = "Old Text" })</span>
In a seperate js file, I want to set the data-helptext
attribute to a string value. Here's my code:
alert($(targetField).data("helptext"));
$(targetField).data("helptext", "Testing 123");
The alert()
call works fine, it shows the text "Old Text" in an alert dialog. However, the call to set the data-helptext
attribute to "Testing 123" does not work. "Old Text" is still the attribute's current value.
Am I using the call to data() incorrectly? I've looked this up on the web, and I can't see what I'm doing wrong.
Here's the HTML markup:
<input data-helptext="Old Text" id="Course_Title" name="Course.Title" type="text" value="" />
It is mentioned in the .data()
documentation
The data- attributes are pulled in the first time the data property is accessed and then are no longer accessed or mutated (all data values are then stored internally in jQuery)
This was also covered on Why don't changes to jQuery $.fn.data() update the corresponding html 5 data-* attributes?
The demo on my original answer below doesn't seem to work any more.
Updated answer
Again, from the .data()
documentation
The treatment of attributes with embedded dashes was changed in jQuery 1.6 to conform to the W3C HTML5 specification.
So for <div data-role="page"></div>
the following is true $('div').data('role') === 'page'
I'm fairly sure that $('div').data('data-role')
worked in the past but that doesn't seem to be the case any more. I've created a better showcase which logs to HTML rather than having to open up the Console and added an additional example of the multi-hyphen to camelCase data- attributes conversion.
Also see jQuery Data vs Attr?
HTML
<div id="changeMe" data-key="luke" data-another-key="vader"></div>
<a href="#" id="changeData"></a>
<table id="log">
<tr><th>Setter</th><th>Getter</th><th>Result of calling getter</th><th>Notes</th></tr>
</table>
JavaScript (jQuery 1.6.2+)
var $changeMe = $('#changeMe');
var $log = $('#log');
var logger;
(logger = function(setter, getter, note) {
note = note || '';
eval('$changeMe' + setter);
var result = eval('$changeMe' + getter);
$log.append('<tr><td><code>' + setter + '</code></td><td><code>' + getter + '</code></td><td>' + result + '</td><td>' + note + '</td></tr>');
})('', ".data('key')", "Initial value");
$('#changeData').click(function() {
// set data-key to new value
logger(".data('key', 'leia')", ".data('key')", "expect leia on jQuery node object but DOM stays as luke");
// try and set data-key via .attr and get via some methods
logger(".attr('data-key', 'yoda')", ".data('key')", "expect leia (still) on jQuery object but DOM now yoda");
logger("", ".attr('key')", "expect undefined (no attr <code>key</code>)");
logger("", ".attr('data-key')", "expect yoda in DOM and on jQuery object");
// bonus points
logger('', ".data('data-key')", "expect undefined (cannot get via this method)");
logger(".data('anotherKey')", ".data('anotherKey')", "jQuery 1.6+ get multi hyphen <code>data-another-key</code>");
logger(".data('another-key')", ".data('another-key')", "jQuery < 1.6 get multi hyphen <code>data-another-key</code> (also supported in jQuery 1.6+)");
return false;
});
$('#changeData').click();
Original answer
For this HTML:
<div id="foo" data-helptext="bar"></div>
<a href="#" id="changeData">change data value</a>
and this JavaScript (with jQuery 1.6.2)
console.log($('#foo').data('helptext'));
$('#changeData').click(function() {
$('#foo').data('helptext', 'Testing 123');
// $('#foo').attr('data-helptext', 'Testing 123');
console.log($('#foo').data('data-helptext'));
return false;
});
Using the Chrome DevTools Console to inspect the DOM, the $('#foo').data('helptext', 'Testing 123');
does not update the value as seen in the Console but $('#foo').attr('data-helptext', 'Testing 123');
does.