JS中计算两个时间相差多少天

function jsGetSjzyts(rysj1,cysj2){
    var returnZyts = 0;
    if( ("" == rysj1)  ||  ("" == cysj2) ) {
        returnZyts = 0;
        $('#sjzyts').prop("value", returnZyts);
        return returnZyts;
    }
    else{   
        var rysjArr = rysj1.split("-");
        var rysjYear = rysjArr[0];
        var rysjMonth = rysjArr[1];
        var rysjDay = rysjArr[2];
        var cysjArr = cysj2.split("-");
        var cysjYear = cysjArr[0];
        var cysjMonth = cysjArr[1];
        var cysjDay = cysjArr[2];
        if((rysjYear == cysjYear) && (rysjMonth == cysjMonth) && (rysjDay == cysjDay)) {
            returnZyts = 0;
            return returnZyts;
         }
         else{
             var data1 = new Date(rysj1);
             var data2 = new Date(cysj2);
             returnZyts = parseInt(Math.abs(data2 - data1) / 1000 / 60 / 60 / 24);
             return returnZyts;
          }
        }
    }