<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, minimum-scale=1.0">
</head>
<body>
<div>
<button id="save" onclick="saveFile()"></button>
</div>
<script>
async function saveFile() {
let e = await self.showSaveFilePicker();
self.entry = e;
return e.name;
}
</script>
</body>
</html>