需要数学日期算法

Question

令人尴尬的是,我需要一个小算法

我正在帮助一个网站,其中gif B在7月1日显示,C在第三个,A在第五个.然后b再次在第七,依此类推 - a,b,c每天早上8点改变

那么我如何使用一个简单的算法使这个脚本返回0,1或2,具体取决于自7月1日以来的天数

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

试试这个:

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]);