How to add a word to the address bar when clicking on a button?

Question

PHP

Guys, such a question - how, when you click on a button, add a word to the address bar.
For example, there is an address mysite.com/about , and when you click on the button, you need to insert the word in this way mysite.com /EN/ about and, most importantly, immediately go to a new page with a new address

Answer 1

window.location.href + replace()