javascript progress redirect fix

Hi i have an easy enough project that needs doing by a js expert i have a page which will be redirected to another page via javascript the destination page will take a certain undefined time to respond ( perhaps a minute, perhaps 30 seconds perhaps 3 minutes) there is a message on the page to let the user know but we also need a number and % which will be incremented every x seconds (this is configured via the js as you will see in example code) therefore 0% (x seconds)….. 5% (x seconds)….. 10% (x seconds)….. 15% i need this incrementation to continue BUT if the destination page is ready then i need the redirect to happen (we cannot reload the page as we will lose the connection with the destination service) the code is 1/2 done and i can and will supply this so you may just need to tweak that code i need the chosen person to deliver this 100% working against payment