How to set HTML5 required attribute in Javascript?

by

required is a reflected property (like id, name, type, and such), so:

element.required = true;

…where element is the actual input DOM element, e.g.:

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

(Just for completeness.)

Re:

Then the attribute’s value is not the empty string, nor the canonical name of the attribute:

edName.attributes.required = [object Attr]

That’s because required in that code is an attribute object, not a string; attributes is a NamedNodeMap whose values are Attr objects. To get the value of one of them, you’d look at its value property. But for a boolean attribute, the value isn’t relevant; the attribute is either present in the map (true) or not present (false).

So if required weren’t reflected, you’d set it by adding the attribute:

element.setAttribute("required", "");

…which is the equivalent of element.required = true. You’d clear it by removing it entirely:

element.removeAttribute("required");

…which is the equivalent of element.required = false.

But we don’t have to do that with required, since it’s reflected.

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