// <ul id="r"></ul> fetch('https://iwb.jp/wp-json/wp/v2/posts?per_page=20') .then(response => response.json()) .then(data => { const r = document.getElementById('r') const html = data.reduce((a, c) => { a.push(c.title.rendered) return a }, []) r.innerHTML = '<li>' + html.join('</li><li>') + '</li>' });