JS　计算两日期时间相差多少天

计算两日期时间相差多少天!

function getDays(DateOne,DateTwo){
		var OneMonth = DateOne.substring(5,DateOne.lastIndexOf ('-')); 
		var OneDay = DateOne.substring(DateOne.length,DateOne.lastIndexOf ('-')+1); 
		var OneYear = DateOne.substring(0,DateOne.indexOf ('-')); 

		var TwoMonth = DateTwo.substring(5,DateTwo.lastIndexOf ('-')); 
		var TwoDay = DateTwo.substring(DateTwo.length,DateTwo.lastIndexOf ('-')+1); 
		var TwoYear = DateTwo.substring(0,DateTwo.indexOf ('-')); 

		var cha=((Date.parse(OneMonth+'/'+OneDay+'/'+OneYear)- Date.parse(TwoMonth+'/'+TwoDay+'/'+TwoYear))/86400000); 
		return Math.abs(cha); 
	}