The observable object to count. In case an array is passed in, a ref to its .length will be returned.
an observable object for which the value property reflects the number of properties in proxied with a value other than undefined.
const items = proxy({x: 3, y: 7} as any);
const cnt = count(items);
// Create a DOM text node for the count:
$('div', {text: cnt});
// <div>2</div>
// Or we can use it in an {@link observe} function:
observe(() => console.log("The count is now", cnt.value));
// The count is now 2
// Adding/removing items will update the count
items.z = 12;
// Asynchronously, after 0ms:
// <div>3</div>
// The count is now 3
Reactively counts the number of properties in an objects.