Hi there Robert Norden!
As you continue learning about JavaScript you will find that several things could help you here including a backend language. You might consider learning about React, which is a JavaScript library and fairly extensive at that. This allows you to break your site into “components” such as navigation, footer, etc. Then for each page you want you would include the navigation as a component. So, if you change the navigation component, then that will be echoed across your site for every page that has the navigation component included.
Just a thought! I’d suggest after delving more deeply into JavaScript and getting a good handle on that, you look at the possibilities of React.
Hope this helps!
edited for additional information
The reason you can’t find a consensus about this is that there are multiple ways to do it