DOMRectList: length property

A positive integer representing the count of DOMRect objects in the DOMRectList. If there are no rectangles in the list, length is 0.

In the following example, we retrieve the list of rectangles for a <div> element using Element.getClientRects(). We then display the number of rectangles in the list within another <div> element on the page.

First, the HTML:

<div id="box" style="width: 50px; height: 20px; border: 1px solid black;"></div>
<div id="output"></div>

Now the JavaScript:

const box = document.getElementById("box");
const rects = box.getClientRects();
const output = document.getElementById("output");

output.textContent = `Number of rectangles: ${rects.length}`;

The output looks like this: