The DOMRectList method item() returns the DOMRect at the specified index within the list, or null if the index is out of range.
item(index)indexA zero-based integer representing the position of the DOMRect in the DOMRectList to retrieve.
A DOMRect object at the specified index in the DOMRectList, or null if index is greater than or equal to the number of rectangles in the list.
const rects = document.getElementById("rects").getClientRects();
console.log(rects.length); // Number of rectangles in the DOMRectList
if (rects.length > 0) {
console.log(rects.item(0)); // Logs the first DOMRect object
}