Redirect with javascript "&" in url

I am trying to use JavaScript for redirecting to affiliate links. The problem is that the url contains & which changes to & after the redirect.

location.href ="http://ift.tt/1DmTnyQ"

will in the web browser be changed to

http://ift.tt/1IDqgD4

With & in the url the affiliate link doesn't work.

How can I fix this problem? encodeURIComponent()?