原生js实现日期联动

月份的判定，由于涉及到过多了判定条件，如果用if else会大大降低性能，建议用switch 语法
代码如下：
复制代码代码如下:
getDays:function（year,month）{
         // var aDay = [31,28|29,31,30,31,30,31,31,30,31,30,31];
        // 二月份的天数数据处理
        var FedDays = year%4==0?29:28,
            returnDays = "";
        var month = month<10?month = "0"+month:month.toString（）;
        switch（month）{
            case "01":
            case "03":
            case "05":
            case "07":
            case "08":
            case "10":
            case "12": returnDays = 31;break;
            case "04":
            case "06":
            case "09":
            case "11": returnDays = 30;break;
            case "02": returnDays = FedDays;break;
        }
        return returnDays;
    }

完整的源代码：
复制代码代码如下:
/* author:laoguoyong
------------------------------
日期三级联动,范围选择
------------------------------
参数
* [String] targets:"#year,#month,#day" ；年，月，日的id
* [String] range:"2013-02-03,2019-09-21"；范围，正确格式为xxxx-xx-xx
----为了节省代码，请传入正确的日期范围参数
----错误示范：
（1）range:"2013-02-03,2019-9-21" 是不对的，注意日期格式
（2）range:"2013-02-03" 是不对的，请输入完整的范围之值
（3）range:"2013-02-03,2016-02-30" 是不对的，2月没有30天
（3）range:"2013-02-03,2011-02-30" 是不对的，范围错误了
*
*/
function GySetDate（opt）{
    //elem
    var targets = opt.targets.split（","）;
    this.eYear = this.getId（targets[0].slice（1））;
    this.eMonth = this.getId（targets[1].slice（1））;
    this.eDay = this.getId（targets[2].slice（1））;
    if（！this.eYear||！this.eMonth||！this.eDay） return;
    //范围值
    var r = opt.range.indexOf（","）,
        aStarts = opt.range.slice（0,r）.split（"-"）, // 转为：["2013","05","20"]
        aEnds = opt.range.slice（r+1,opt.range.length）.split（"-"）; // 转为：["2018","08","20"]
    //Number类型
    this.startYear = parseInt（aStarts[0],10）;
    this.startMonth = parseInt（aStarts[1],10）;
    this.startDay = parseInt（aStarts[2],10）;
    this.endYear = parseInt（aEnds[0],10）;
    this.endMonth = parseInt（aEnds[1],10）;
    this.endDay = parseInt（aEnds[2],10）;
    this.init（）;
}
GySetDate.prototype = {
    init:function（）{
        var _that = this;
        // 初始化日期
        this.setYears（{"start":this.startYear,"end":this.endYear}）;
        this.setMonths（{"start":this.startMonth}）;
        this.setDays（{"year":this.startYear,"month":this.startMonth,"start":this.startDay}）;
        // 年选择
        this.eYear.onchange = function（）{
            var year = parseInt（this.value）;
            switch（true）{
                case （year == _that.startYear）:{
                    _that.setMonths（{"start":_that.startMonth}）;
                    _that.setDays（{"year":_that.startYear,"month":_that.startMonth,"start":_that.startDay}）;
                };break;
                case （year == _that.endYear）:{
                    _that.setMonths（{"start":1,"end":_that.endMonth}）;
                    if（_that.endMonth>1）{
                        _that.setDays（{"year":_that.endYear,"month":1,"start":1}）;
                    }else{
                        _that.setDays（{"year":_that.endYear,"month":1,"start":1,"end":_that.endDay}）;
                    }
                };break;
                default:{
                    _that.setMonths（{"start":1}）;
                    _that.setDays（{"start":1,"year":year,"month":1}）;
                }
            }

        }
        // 月选择
        this.eMonth.onchange = function（）{
            var year = parseInt（_that.eYear.options[_that.eYear.selectedIndex].value）,
                month = parseInt（this.value）;
            switch（true）{
                case （year==_that.endYear&&month==_that.endMonth）:{
                    _that.setDays（{"start":1,"year":year,"month":month,"end":_that.endDay}）;
                };break;
                case （year==_that.startYear&&month==_that.startMonth）:{
                    _that.setDays（{"year":_that.startYear,"month":_that.startMonth,"start":_that.startDay}）;
                };break;
                default:{
                    _that.setDays（{"start":1,"year":year,"month":month}）;
                }
            }

        }
    },
    /*设置年，月，日
    ----------------------------------
    参数值都为Number类型
    */
    // 参数 {"start":xx,"end":xxx}
    setYears:function（opt）{
        this.eYear.innerHTML = "";
         for（var n=opt.start;n<=opt.end;n++）{
            this.eYear.add（new Option（n,n））;
        }
    },
    // 参数 {"start":xx,"end":xxx}
    // 参数 "end" 为可选，忽略，则开始到12月
    setMonths:function（opt）{
        this.eMonth.innerHTML = "";
        var months = opt.end || 12;
        for（var n=opt.start;n<=months;n++）{
            if（n<10） n = "0"+n;
           this.eMonth.add（new Option（n,n））;
        }
    },
    // 参数 {"start":xx,"year":xxx,"month":xx,"star":xx,"end":xxx}
    // 参数 "end" 为可选，忽略，则开始到本月底（根据月份判断的）
    setDays:function（opt）{
         this.eDay.innerHTML = "";
         var days = opt.end || this.getDays（opt.year,opt.month）;
         for（var n=opt.start;n<=days;n++）{
            if（n<10） n = "0"+n;
            this.eDay.add（new Option（n,n））;
         }
    },
    /* 根据年，月，返回正确的天数，如 2016-2，返回是29天（润年）
    --------------------------------------------------------------
    参数值都为Number类型
    */
    getDays:function（year,month）{
         // var aDay = [31,28|29,31,30,31,30,31,31,30,31,30,31];
        // 二月份的天数数据处理
        var FedDays = year%4==0?29:28,
            returnDays = "";
        var month = month<10?month = "0"+month:month.toString（）;
        switch（month）{
            case "01":
            case "03":
            case "05":
            case "07":
            case "08":
            case "10":
            case "12": returnDays = 31;break;
            case "04":
            case "06":
            case "09":
            case "11": returnDays = 30;break;
            case "02": returnDays = FedDays;break;
        }
        return returnDays;
    },
    /*工具辅助函数
    ----------------------------------
    */
    getId:function（id）{
        return document.getElementById（id）;
    }
}

效果展示图：

效果还不错吧，小伙伴们自己美化下，使用到自己的项目中去吧。