The keys() method of the DOMTokenList interface returns an iterator allowing to go through all keys contained in this object. The keys are of type unsigned integer.





Return value

Returns an iterator.


In the following example we retrieve the list of classes set on a <span> element as a DOMTokenList using Element.classList. We when retrieve an iterator containing the keys using values(), then iterate through those keys using a for ... of loop, writing each one to the <span>'s Node.textContent.

First, the HTML:

<span class="a b c"></span>

Now the JavaScript:

var span = document.querySelector("span");
var classes = span.classList;
var iterator = classes.keys();

for(var value of iterator) {
  span.textContent += value + ' ++ ';

The output looks like this:


Specification Status Comment
The definition of 'keys() (as iterable<Node>)' in that specification.
Living Standard Initial definition

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes ?50 ? Yes ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes ?50 Yes ? ?

Document Tags and Contributors

 Contributors to this page: fscholz, chrisdavidmills, teoli
 Last updated by: fscholz,