I want to check if an HTML5 data attribute exists using plain javascript. I have tried the below code snippet, but it doesn't work.
if(object.getAttribute("data-params")==="undefined") {
//data-attribute doesn't exist
}
Element.getAttribute
returns null
or empty string if the attribute does not exist.
You'd use Element.hasAttribute
:
if (!object.hasAttribute("data-example-param")) {
// data attribute doesn't exist
}
or Element.dataset
(see also: in
operator ):
if (!("exampleParam" in object.dataset)) {
// data attribute doesn't exist
}
or even
if (!object.getAttribute("data-example-param")) {
// data attribute doesn't exist or is empty
}
Checking against null also yielded the solution.
if (object.getAttribute("data-example-param") === null) {
//data attribute doesn't exist
}else{
//data attribute exists
}
The code you posted doesn't won't work as you expect, what you're doing here is checking if the attribute-value of the named attribute ( "data-params"
) is equal to "undefined"
, which will return true
only if the attribute is data-params="undefined"
.
if (object.getAttribute("data-params") === "undefined") {
// the "data-params" attribute-value is exactly "undefined"
// note that `getAttribute()` is a
}
What I suspect you want to do is:
var typeOfObjectAttribute = typeof object.getAttribute("data-params");
if (typeOfObjectAttribute === null || typeOfObjectAttribute === "") {
// data-params attribute doesn't exist on that Node.
}
Note that – according Mozilla Developer Network (at the reference for Element.getAttribute()
, below) – states that:
getAttribute()
returns the value of a specified attribute on the element. If the given attribute does not exist, the value returned will either benull
or""
(the empty string)…
It's also worth noting that getAttribute()
is a method of the Element nodes, rather than generic objects.
Incidentally, you could also use the following approach (again, testing that the attribute is not set):
// here we look to see if the 'params' key is present in the
// HTMLElement.dataset object of the element, and then invert
// that result using the '!' operator, to check that the
// attribute *isn't* present:
if (!('params' in document.getElementById('elementID').dataset)) {
// the data-params attribute is not present.
}
References:
You could as well just use the dataset API.
The HTMLElement.dataset read-only property allows access, both in reading and writing mode, to all the custom data attributes (data-*) set on the element. It is a map of DOMString, one entry for each custom data attribute.
Sadly this will not work in IE10 but i am pretty sure that there is a shim out there somewhere.
Here is an example
var containerData = document.querySelector('#container').dataset, contentData = document.querySelector('#content').dataset; // Check if dataset is empty or not. console.log(Object.keys(containerData).length === 0); console.log(Object.keys(contentData).length === 0); // Check for specific data if (containerData.hasOwnProperty('bar')) { console.log(containerData.bar); } // Here is the dataset console.log(containerData);
<div id="container" data-foo="bar" data-bar="foo"> <div id="content"> Content </div> </div>
Try using typeof :
if(typeof object.getAttribute("data-params") === "undefined") {
console.log('data-attribute doesn't exist');
}
You cang do just falsy value check
if(!object.getAttribute("data-params")) {
//data-attribute doesn't exist
}
cause getAttribute
can return null or empty string
also you can use object.hasAttribute("data-params")
just to check if attribute exists
The only thing that worked well for me was this.
if(typeof object.dataset.sheet === "undefined") {
console.log('Data attribute does not exist');
}
Even more simple:
if (object.dataset.sheet !== undefined) {
// the "data-sheet" attribute exists
}
To see if a given HTML5 element has a specific custom HTML5 data-*
attribute, simply examine the element's dataset
.
A dataset
is a DOMStringMap
object so you can use the hasOwnProperty()
method:
if (element.dataset.hasOwnProperty('params')) {
[... CODE HERE...]
}
If anyone landed here knowing what data attribute they are looking for then you can check if it exists with
HTML:
<input id="your-element" data-type="something">
JS:
const element = document.querySelector('#your-element');
if( element.dataset.type === 'something'){
// Do something
}
Of course the type
in data-type
in the example above is a custom name, data attributes can have any name such as data-cats
or data-dogs
etc.. ... ...
您可以使用matches()
方法,选择器的工作方式与查询选择器的工作方式相同
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