DOMTokenList.keys()

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

Syntax

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 then retrieve an iterator containing the keys using keys(), 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:

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

for(let value of iterator) {
  span.textContent += `(${value}) `;
}

The output looks like this:

Specifications

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Browser compatibility

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See also