JavaScript 日期差异

我在使用 DateDiff 函数时遇到问题。我试图找出两个日期/时间之间的差异。我读过这篇文章（在Javascript中计算日期差异的最佳方法是什么）我还看了这个教程（http://www.javascriptkit.com/javatutors/datedifference.shtml）但我似乎无法理解。

这是我试图开始工作但没有成功的事情。有人可以告诉我我在做什么以及如何简化它。似乎有点编码过多......？

//Set the two dates
var currentTime = new Date();
var month = currentTime.getMonth() + 1;
var day = currentTime.getDate();
var year = currentTime.getFullYear();
var currDate = month + "/" + day + "/" + year;
var iniremDate = "8/10/2012";

//Show the dates subtracted
document.write('DateDiff is: ' + currDate - iniremDate);

//Try this function...
function DateDiff(date1, date2) {
    return date1.getTime() - date2.getTime();
}

//Print the results of DateDiff
document.write (DateDiff(iniremDate, currDate);

对于那些想要一个工作示例的人来说，这里是一个简单的 DateDiff ex，它以负值（日期已过）或正值（日期即将到来）告诉日期差异。

编辑：我更新了这个脚本，所以它会为你做一些跑腿工作，并将结果转换为 -10，这意味着日期已经过去。输入您自己的 currDate 和 iniPastedDate 日期，您应该可以开始了！

//Set the two dates
var currentTime   = new Date()
var currDate      = currentTime.getMonth() + 1 + "/" + currentTime.getDate() + "/" + currentTime.getFullYear() //Todays Date - implement your own date here.
var iniPastedDate = "8/7/2012" //PassedDate - Implement your own date here.

//currDate = 8/17/12 and iniPastedDate = 8/7/12

function DateDiff(date1, date2) {
    var datediff = date1.getTime() - date2.getTime(); //store the getTime diff - or +
    return (datediff / (24*60*60*1000)); //Convert values to -/+ days and return value      
}

//Write out the returning value should be using this example equal -10 which means 
//it has passed by ten days. If its positive the date is coming +10.    
document.write (DateDiff(new Date(iniPastedDate),new Date(currDate))); //Print the results...