Create file and force download

by Stalk

HTML

<form name="test">
  <textarea name="content">
    <item>
      <product>тестирование</product>
      <category>еще тест</category>
    </item>
    <item>
      <product>тестирование</product>
      <category>еще тест</category>
    </item>
  </textarea>
</form>

JavaScript

let str = document.querySelector('form textarea[name="content"]').value
let xml = `<?xml version="1.0" ?><root>${str}<root></xml>`

let blob = new Blob([xml], {type: "text/xml"}),
    url = window.URL.createObjectURL(blob);

let a = document.createElement("a");
a.style.display = 'none'
a.href = url
document.body.appendChild(a)
a.download = 'myXML.xml';
a.click()
window.URL.revokeObjectURL(url);