Extending templates/web.html in a custom vuejs web page/app throws: "Uncaught SyntaxError: Identifier 'app' has already been declared"

extending templates/web.html in a custom vuejs web page/app throws: “Uncaught SyntaxError: Identifier ‘app’ has already been declared”

Not working:

{% extends “templates/web.html” %} {% block content %}

“My Vuejs app”

{% endblock %}

Issue:
Uncaught SyntaxError: Identifier ‘app’ has already been declared

Working:

{% block content %}

“My Vuejs app”

{% endblock %}

basically, if i don’t extend the web page from templates/web.html, it is working fine, how else should i extend web.html?

note: if i don’t extend from web.html, the default template like the navbar, footer dont appear and i’m not able to use frappe object as well