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Setting an attribute named “required” and any value, with JQuery, doesn't work

Posted by: admin January 2, 2018 Leave a comment

Questions:

This doesn’t work:

$("#elementId").attr("required", "true");

In both Chrome and Firefox, the DOM produces either required as the attribute (no value) or required="" (empty value).

And it doesn’t matter that the value in this example is “true”. If you try “asdf” the same thing happens.

What’s odd is that I believe this used to work because this new code is part of a large project that’s been ongoing for several years.

The only thing I can think of is that my Chrome (v10) and Firefox (v4) are now both sufficiently advanced that they’re recognizing the required attribute as an HTML5 reserved keyword. I added the novalidate attribute, thinking that that might turn off any form-related HTML5-ness. No such luck.

Thoughts?

Edit:

To clarify, this only happens with JQuery. If I say this, it works:

$("#elementId")[0].setAttribute("required", "true");

Is there a bug in JQuery? Any idea why this only happens with JQuery? Our development team likes all code to go through JQuery where possible. I can use the straight setAttribute JavaScript method, but would rather use a JQuery solution that works.

Edit 2:

The crux of the matter is this…

Why does using JQuery’s attr() method not work when the regular setAttribute() method does? Doesn’t the attr() method call setAttribute() at some point lower down?

That is what is so confusing. Chrome and Firefox are perfectly fine setting required="true" if you use setAttribute().

Answers:

It is indeed browser related. I checked in IE8 and it will apply whatever string value you set to the required attribute.

Since you don’t need any value (only the attribute must be present), this won’t affect default behavior. If you are abusing the attribute value for javascript hooks, that’s another thing 🙂

<input required> is the same as <input required=""> and <input required="honky-tonk">

Since IE8 doesn’t support html5, it’s just like setting a made-up attribute, so you could set $("input").attr("derp", "derty") and it would assign it to the element.

My guess is that jquery uses the required="" for folks who wish to use this in XHTML strict syntax, while still conforming to HTML5 standards.

http://dev.w3.org/html5/spec/Overview.html#the-required-attribute

http://dev.w3.org/html5/spec/Overview.html#boolean-attribute

Questions:
Answers:

You can use prop to achieve this:

$("#elementId").prop("required", true);

Corresponding documentation: http://jquery.com/upgrade-guide/1.9/#attr-versus-prop-

Questions:
Answers:

The way I got this working was to implement the following good old javascript in place of any jQuery:

document.getElementById("inputid").required = true;

or, (obviously)

document.getElementById("inputid").required = false;

depending on requirements.

The source of my solution is here.

I have read through .attr() and .prop() pages on the jQuery API, and there seems to be no support for the “required” attribute – but I am open to correction.

Questions:
Answers:

I use this fairly often and I haven’t noticed any problems with it.

$("#elementId").attr("required", "required");

Note: I have try this but I could NOT get it working:

$("#elementId").attr("required");

Even though required is now a boolean attribute, simply adding the attribute name (without the value) does not appear to be too compatible with different versions of different browsers. Stick with my original example above and you should be fine.

Questions:
Answers:

For input required, it works much better if you remove the attribute vs. setting it to false

$('#elementId').removeAttr('required');