Append logo text from different html pages

I have created my logo based on html text.
In the main page, the logo is: x.
when I navigate to a subpage, I need to append my logo to be: x.y, so only y should be added with the same color of the point (the dot).

https://i.sstatic.net/xCDku7iI.png

Can someone help me, how can I achieve that using js?
Thank you