Extra tag or mark in single page

[un4gt]

Is it possible to add additional tags to a page and get the added tags in the page through the event handler in the html-page-context event?
I want to check if some pages have the tags I added, and if so add some javascript code . Like below :

def insert_javascript_on_marked_page(app, page_name, template_name, context, doctree):
    # TODO

def setup(app):
    app.connect('some_event', insert_javascript_on_marked_page)

[SilverRainZ]

You can add custom File-wide metadata to the page, and access them through app.env.metadata[docname].