JSFiddle - React, Tailwind, and code Playground

HTML

<h2 id="one"></h2>
<h2 id="two"></h2>

JavaScript

var myObject = {items: {0: {k: 1}, 1: {k: 2}}};

var myArray = [{k: 1}, {k: 2}];

document.getElementById('one').innerHTML = myObject.items.length;
document.getElementById('two').innerHTML = myArray.length;