How to add menu to all custom pages of a module

I made 2 custom pages now i want to add menu to all the pages
I made the custom page using page doctype

Each custom page has html,css,js and py file associated with it
html file

css file

js file

and also a python file which is mainly used for the purpose of context or server side script and
mainly javascript is used for rendering, so is there any why i can render another html file (which is of menu) along with the above html file using javascript so that the above page can have menu