javascript get org name from URL

hi

I am trying to create a URL that navigates to contact, but the URL needs to be dynamics so it works in dev, test and prod.

Example:

DEV URL https://martind.crm4.dynamics.com/main.aspx#276111347

PROD URL https://prod.crm4.dynamics.com/main.aspx#276111347

How can I retrive the orgname? (martind, and prod) from the link with js and put it in a dynamicURL?

Thanks for answers