javascript比较时间范围

function checkSelect(){
                var begindate = document.getElementById("beginTime").value;
                var enddate = document.getElementById("endTime").value;
                if(begindate==null || begindate == ""){
                    document.getElementById("beginTime").focus();
                        alert("开始时间不能为空，请重新输入");
                        return false;
                }
                if(enddate==null || enddate == ""){
                    document.getElementById("endTime").focus();
                        alert("结束时间不能为空，请重新输入");
                        return false;
                }
                var v_begin = begindate.split("-");
                var v_end = enddate.split("-");
                convCheck(v_begin,v_end);
        }

        // 将时间格式化成YYYYMMDD
        function check(date){
                var v_year = date[0];
                var v_month = date[1];
                var v_day = date[2];
                var temp1 = v_year+v_month+v_day;
                return temp1;
        }

        // 比较时间范围
        function convCheck(begin,end){
                var beginTime  = Number(check(begin));
                var endTime = Number(check(end));
                if((beginTime - endTime)>0){
                        alert("选择的结束时间应该大于开始时间，请重新选择");
                        document.getElementById("endTime").value="";
                        document.getElementById("endTime").focus();
                        return false;
                }
                if((endTime - beginTime)/100>3){
                        alert("您选择的时间不能超过三个月，请重新选择");
                        document.getElementById("endTime").value="";
                        return false;
                }else{
                        alert("时间在三个月允许的范围内");
                }
        }