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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.

Syntax

tokenList.keys();

Parameters

None.

Return value

Returns an iterator.

Examples

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:

Specifications

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

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
keysChrome Full support 45Edge ? Firefox Full support 50IE ? Opera Full support 32Safari ? WebView Android Full support 45Chrome Android Full support 45Edge Mobile ? Firefox Android Full support 50Opera Android Full support 32Safari iOS ? Samsung Internet Android Full support Yes

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

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