js 判断日期间隔不超过31天

                        var first = $('#startTime').val();
                        var second = $('#endTime').val();
                        var data1 = Date.parse(first.replace(/-/g,   "/"));
                        var data2 = Date.parse(second.replace(/-/g,   "/"));
                        var datadiff = data2-data1;
                        var time = 31*24*60*60*1000;
                        if(first.length>0 && second.length>0){
                            if(datadiff<0||datadiff>time){
                                alert("开始时间应小于结束时间并且间隔小于31天，请检查!");
                                return false;
                            }
                        }