</th><td>
<input type="text" name="email" id="email" class="required email" value="demo@mail.ru" />
</td></tr>
<tr><th>
<label for="createdate">Дата покупки</label>
const html = `<td>
<input type="text" name="email" id="email" class="required email" value="demo@mail.ru" />
</td>`
const template = document.createElement('template')
template.innerHTML = html
console.log(template.content.querySelector('input[name="email"]').value) // demo@mail.ru
let m= document.body.innerHTML.match(/(?=[^>]*name="email")<input[^>]+value="([^"]+)"/is);
console.log(m[1]);