<html><body>
<a download="9dksk239xwd.txt" id="test" href="#">test</a>
<script type="application/javascript">
var type = 'data:text/plain;charset=UTF-8, ';
var text = "строка1 \n строка2";
var res = type+text;
document.getElementById('test').href = res;
</script>
</body></html>
Простой
