Well, finally I left vue with Pas2js due I can't find the way. But made the same Vue.js demo in no time with regular Pas2js.
program pas2jsvue;
{$mode objfpc}
uses
JS,
Classes,
SysUtils,
StrUtils,
Web;
var
message: TJSElement;
button1: TJSElement;
begin
message := document.getElementById('message');
button1 := document.getElementById('button1');
button1.addEventListener('click', procedure
begin
message.innerText := ReverseString(message.innerText);
end);
end.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Pas2JS Vue</title>
</head>
<body>
<div id="app">
<p id='message'>Hello World</p>
<button id='button1'>Reverse Message</button>
</div>
<script src="./pas2jsvue.js"></script>
<script>
rtl.run();
</script>
</body>
</html>