The value property of the DOMTokenList interface is a stringifier that returns the value of the list serialized as a string, or clears and sets the list to the given value.

A string representing the serialized content of the list. Each item is separated by a space.

In the following example we retrieve the list of classes set on a <span> element as a DOMTokenList using Element.classList, then write the value of the list 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;
span.textContent = classes.value;

The output looks like this: