dropdownlist绑定日期,用Jquery检测起始日期,终止日期合法性

有4个dropdownlist分别是起始年，起始月，终止年，终止月

由于项目要示年的dropdownlist只需绑定当年前的前三年后两年如,2005,2006......

月的dropdownlist绑定1-12

下面是实现代码

        $(function() {
            $('#ddlYearEnd').change(function() {
                var endYear = $(this).val();
                var beginYear = $('#ddlYear').val();
                if (parseFloat(endYear) < parseFloat(beginYear)) {
                    $(this).val(beginYear);
                    alert('起始年不可大于终止年!');
                }
                var endMonth = $('#ddlMonthEnd').val();
                var beginMonth = $('#ddlMonth').val();
                if (parseFloat(endYear) == parseFloat(beginYear))
                    if (parseFloat(endMonth) < parseFloat(beginMonth)) {
                        $('#ddlMonthEnd').val(beginMonth);
                    alert('起始月不可大于终止月!');
                }
            })
            $('#ddlYear').change(function() {
                var endYear = $('#ddlYearEnd').val();
                var beginYear = $(this).val();
                if (parseFloat(endYear) < parseFloat(beginYear)) {
                    $(this).val(endYear);
                    alert('起始年不可大于终止年!');
                }
                var endMonth = $('#ddlMonthEnd').val();
                var beginMonth = $('#ddlMonth').val();
                if (parseFloat(endYear) == parseFloat(beginYear))
                    if (parseFloat(endMonth) < parseFloat(beginMonth)) {
                        $('#ddlMonth').val(endMonth);
                    alert('起始月不可大于终止月!');
                }
            })
            $('#ddlMonthEnd').change(function() {            
                var beginYear = $('#ddlYear').val();
                var endYear = $('#ddlYearEnd').val();
                var endMonth = $(this).val();
                var beginMonth = $('#ddlMonth').val();
                if (parseFloat(endYear) == parseFloat(beginYear))
                    if (parseFloat(endMonth) < parseFloat(beginMonth)) {
                        $(this).val(beginMonth);
                    alert('起始月不可大于终止月!');
                }
            })
            $('#ddlMonth').change(function() {
                var beginYear = $('#ddlYear').val();
                var endYear = $('#ddlYearEnd').val();
                var endMonth = $('#ddlMonthEnd').val();
                var beginMonth = $(this).val();
                if (parseFloat(endYear) == parseFloat(beginYear))
                    if (parseFloat(endMonth) < parseFloat(beginMonth)) {
                        $(this).val(endMonth);
                    alert('起始月不可大于终止月!');
                }
            })
        })