Unable to set data attribute using jQuery Data() API

user_127440 0
Viewed 133268

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="" />
custom-data-attribute model-view-controller attributes jquery
7 Answers

Happened the same to me. It turns out that 

var data = $("#myObject").data();

gives you a non-writable object. I solved it using:

var data = $.extend({}, $("#myObject").data());

And from then on, data was a standard, writable JS object.

user_20166860

As mentioned, the .data() method won't actually set the value of the data- attribute, nor will it read updated values if the data- attribute changes.

My solution was to extend jQuery with a .realData() method that actually corresponds to the current value of the attribute:

// Alternative to .data() that updates data- attributes, and reads their current value.
(function($){
  $.fn.realData = function(name,value) {
      if (value === undefined) {
        return $(this).attr('data-'+name);
      } else {
        $(this).attr('data-'+name,value);
      }
  };
})(jQuery);

NOTE: Sure you could just use .attr(), but from my experience, most developers (aka me) make the mistake of viewing .attr() and .data() as interchangeable, and often substitute one for the other without thinking. It might work most of the time, but it's a great way to introduce bugs, especially when dealing with any sort of dynamic data binding. So by using .realData(), I can be more explicit about the intended behavior.

user_1656730
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