Javascript dropdown and switching content without page reload

There are two pages,

folder/india.html
folder/usa.html
and dropdown menu in each page to switch between india and usa pages.

india.html page sells in INR and usa.html in USD with links to shopping carts for each currency.

link1(INR)
link2(USD)

Except the link and the currency information(selling price), contents in both the pages are same.

So here comes the problem. Google hates duplicate pages!

I am looking for a solution where,

  • a single page
  • In That Page, a dropdown menu to select currency
  • As the currency is selected, without page reload, the link to shopping cart and the pricing also should be changed according to the selected currency.
  • So Single page should be able to handle both the currencies.

Kindly suggest me with codes as I am new to javascript. Thanks a lot