Question

Embarrassingly enough I need a small algorithm

I am helping with a site where gif B is shown on the first of July, C on the third and A on the fifth. Then b again on the seventh and so on – a,b,c changing every second day at 8 in the morning

So how do I use a simple algo to make this script return 0, 1 or 2 depending on how many days since the 1st of July

http://jsfiddle.net/mplungjan/T2Tjh/

var startDate = new Date(2012,6,1,8,0,0); 
var pics = ["b.gif","c.gif","a.gif"];
var aDay = 24*60*60*1000;
function getDateDiff(startDate,endDate) {
  var diff = endDate.getTime() - startDate.getTime();
  return Math.round(diff/aDay);
}
document.write('<br/>'+getDateDiff(startDate,new Date()));

Answer 1

Try this:

var startDate = new Date(2012, 6, 1, 8, 0, 0);
var pics = ["b.gif", "c.gif", "a.gif"];
var aDay = 24 * 60 * 60 * 1000;

function getDateDiff(startDate, endDate) {
    var diff = endDate.getTime() - startDate.getTime();
    return Math.round(diff / aDay);
}
document.write('<br/>' + pics[Math.floor(getDateDiff(startDate, new Date()) / 2) % 3]);