Javascript Routing with '#' or not? [on hold]

I want to start a project. In this project I want to create an Application with a mainwindow which contains several buttons or links. Every button or link should navigate me to a certain Application. An Application could be a calculator for example.

So instead of refreshing the URL, I want to use the JS-Routing function (without a framework). So which way do you recommend ?

Should I use Routing with '#' like

    <a href='#app1' > App1 </a>

?

Or should I do it without a JS-Router ?

Thank you.