DomTokenList.length is used to show how long the selected element or variable (could be more but i don’t know yet) is. For example we could use it to see how many elements are in an array using array.length; or in the example below see how long an elements name is.

HTML

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

JS

const span = document.querySelector("span");
const classes = span.classList;
const length = classes.**length**;
console.log(length);
//the output is 3 which is how many classes the span element has.

Example #2

const arr = ["I", "Wanna", "Be", "a", "Programmer!"];
const check = arr.**length;**
console.log**(**check**);**
//The output should be 5 since that's how many elements (or strings) are in the array