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I have an element that has an HTML5 data attribute with no value but just the key like this:

<div id="1" data-foo>Foo</div>

If I use dataset like this:

getElementById("1").dataset.foo

then, this will return a null value, and I cannot distinguish whether the element has data-foo attribute or not. Is there are way to check if the element has a data-foo attribute regardless of whether it has a specified value?

I have an element that has an HTML5 data attribute with no value but just the key like this:

<div id="1" data-foo>Foo</div>

If I use dataset like this:

getElementById("1").dataset.foo

then, this will return a null value, and I cannot distinguish whether the element has data-foo attribute or not. Is there are way to check if the element has a data-foo attribute regardless of whether it has a specified value?

• javascript
• html

Share Improve this question Follow asked Feb 9, 2015 at 22:02 sawasawa 168k5050 gold badges286286 silver badges397397 bronze badges

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2 Answers 2

Sorted by: Reset to default 7

You can acplish this by checking if the element contains the attribute using the hasAttribute method:

document.getElementById('1').hasAttribute('data-foo')

If the element does not feature the data-foo attribute, a call to dataset.foo will return undefined, rather than null (or an empty string in the case of an empty attribute).

You should check the actual value, as follows:

var fooVal = document.getElementById('div1').dataset.foo;

// data-foo is not present at all:
if( fooVal === undefined )
{

} 

// data-foo is present but empty
if( fooVal === '' )
{

} 

Of course, you could cast the logic to a simple boolean:

var hasFoo = ( document.getElementById('div1').dataset.foo !== undefined );

jsFiddle Demo

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