DOMTokenList: keys() method
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
js
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:
html
<span class="a b c"></span>
Now the JavaScript:
js
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: