sharepoint 2013 get ID of a user

Hi

I am looking to figure out a way to get the ID of a user, given their name, so that I can use it in a call to /_layouts/15/userdisp?ID=n where 'n' is the ID of the user to redirect the person who is viewing the page to another person's Profile page.  I am using JavaScript. I will not know the url of the mysites site hence using this method rather than the one using the MySites method.  I am on a search results page not a person search results page.

I am using SharePoint 2013 SP1 April 2015 CU.

Thanks Nigel

Nigel Price NJPEnterprises