JS计算两个日期之间相差的年份

//startDateStr(2017-02-22) endDateStr(2018-02-21)
function getDateYearSub(startDateStr, endDateStr) {
var day = 24 * 60 * 60 *1000;

var sDate = new Date(Date.parse(startDateStr.replace(/-/g, "/")));
var eDate = new Date(Date.parse(endDateStr.replace(/-/g, "/")));

//得到前一天(算头不算尾)
sDate = new Date(sDate.getTime() - day);

//获得各自的年、月、日
var sY  = sDate.getFullYear();
var sM  = sDate.getMonth()+1;
var sD  = sDate.getDate();
var eY  = eDate.getFullYear();
var eM  = eDate.getMonth()+1;
var eD  = eDate.getDate();

if(eY > sY && sM == eM && sD == eD) {
return eY - sY;
} else {
alert("两个日期之间并非整年，请重新选择");
return 0;
}
}