Untitled

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Hello, World</title>
</head>
<body>
<p>Hello, <span id="username"></span></p>
<script>
    var user = JSON.parse('{{ user | tojson | safe}}');
    document.getElementById('username').innerHTML=user.firstname + " " +
            user.lastname;

</script>
</body>
</html>