``` const items = reactive([]); const length = derive(() => Object.keys(items).length); return div( list(div, items, ({ val: v }, deleter) => div(() => v, div({ onclick: deleter }, "❌")) ), div(() => `You have ${length.val} item(s)`), span(() => Object.keys(stateFields(items)).length), button({ onclick: () => items.push(items.length + 1) }, "Add Item") ) ``` Both of these values are always `0`