javascript中Date对象应用之简易日历实现

<div class="box">
 <header class='control'>
 <input id="conYear" class="con-in" type="number" min="1900" max="2100" step="1"/>
 <input id="conMonth" class="con-in" type="number" min="1" max="12" step="1"/>
 </header>
 <div class="DateBox">
 <header class='week'>
 <div class="week-in">周日</div>
 <div class="week-in">周一</div>
 <div class="week-in">周二</div>
 <div class="week-in">周三</div>
 <div class="week-in">周四</div>
 <div class="week-in">周五</div>
 <div class="week-in">周六</div>
 </header>
 <section class="dayBox" id='dayBox'>
 <div class="day" id="day1">1</div>
 <div class="day">2</div>
 <div class="day">3</div>
 <div class="day">4</div>
 <div class="day">5</div>
 <div class="day">6</div>
 <div class="day">7</div>
 <div class="day">8</div>
 <div class="day">9</div>
 <div class="day">10</div>
 <div class="day">11</div>
 <div class="day">12</div>
 <div class="day">13</div>
 <div class="day">14</div>
 <div class="day">15</div>
 <div class="day">16</div>
 <div class="day">17</div>
 <div class="day">18</div>
 <div class="day">19</div>
 <div class="day">20</div>
 <div class="day">21</div>
 <div class="day">22</div>
 <div class="day">23</div>
 <div class="day">24</div>
 <div class="day">25</div>
 <div class="day">26</div>
 <div class="day">27</div>
 <div class="day">28</div>
 <div class="day">29</div>
 <div class="day" id="day30">30</div>
 <div class="day" id="day31">31</div>
 </section>
 </div> 
</div>

body{
 margin: 0;
}
input{
 border: none;
 padding: 0;
}
.box{
 width: 354px;
 margin: 30px auto 0; 
}
.DateBox{
 height: 300px;
 border: 2px solid black;
} 
.week{
 overflow: hidden;
 border-bottom: 1px solid black;
 line-height: 49px;
}
.week-in{
 height: 49px;
 float: left;
 width: 50px;
 text-align: center;
}
.dayBox{
 overflow: hidden;
}
.day{
 float: left;
 height: 50px;
 width: 50px;
 font:20px/50px '微软雅黑';
 text-align: center;
}
.control{
 overflow: hidden;
}
.con-in{
 height: 50px;
 float: left;
 width: 100px;
 text-align: center;
 font: 20px/50px "微软雅黑";
}

//准备:获取当前样式
function getCSS(obj,style){
 if(window.getComputedStyle){
 return getComputedStyle(obj)[style];
 }
 return obj.currentStyle[style];
}

//实现一：获取当月的天数，及当月第一天、第30日、第31日是星期几
function get_data(year,month){
 var result = {};
 var d = new Date();
 //如果是2月
 if(month == 2){
 //如果是闰年
 if((year % 4 === 0 && year % 100 !== 0) || year % 400 === 0){
 result.days = 29;
 //如果是平年
 }else{
 result.days = 28;
 }
 //如果是第4、6、9、11月
 }else if(month == 4 || month == 6 ||month == 9 ||month == 11){
 result.days = 30;
 }else{
 result.days = 31;
 //当月第31天是星期几
 result.day31week = d.getDay(d.setFullYear(year,month-1,31));
 }
 //当月第一天是星期几
 result.day1week = d.getDay(d.setFullYear(year,month-1,1));
 if(month != 2){
 //当月第30天是星期几
 result.day30week = d.getDay(d.setFullYear(year,month-1,30)); 
 }
 return result;
}

//实现二：根据当月第一天的星期x，设置第一天的margin-left=宽度*x，使其对应到正确的星期位置上
function move_day1(year,month){
 var week1 = get_data(year,month).day1week;
 day1.style.marginLeft = week1%7*parseInt(getCSS(day1,'width'))+ 'px';
}

//实现三：根据当月的天数，来隐藏多余的天数。当然首先要先显示在其他月份被隐藏的天数
function hide_days(year,month){
 //恢复其他月份可能隐藏的天数
 for(var i = 28; i<31; i++){
 dayBox.children[i].style.display = 'block';
 } 
 //隐藏当月多余的天数
 var days = get_data(year,month).days;
 for(var i = days;i<31;i++){
 dayBox.children[i].style.display = 'none';
 }
};

//实现四：如果当月30日或31日是星期日，则会新占一行，通过设置margin-top把新占一行的天移动到第一行
function move_day30(year,month){
 //如果当月30日是星期日
 if(get_data(year,month).day30week === 0){
 day30.style.marginTop = parseInt(getCSS(day30,'height')) *(-5) + 'px';
 day31.style.marginTop = parseInt(getCSS(day31,'height')) *(-5) + 'px';
 day31.style.marginLeft= getCSS(day31,'width');
 return;
 }else{
 day30.style.marginTop = day31.style.marginTop = day31.style.marginLeft ='0';
 }
 //如果当月31日是星期日
 if(get_data(year,month).day31week === 0){
 day31.style.marginTop = parseInt(getCSS(day31,'height')) *(-5) + 'px';
 }else{
 day31.style.marginTop = '0';
 }
}

//实现五：当载入页面时，获取当前年和月，显示当月日历；当改变年或月时，获取改变后的年和月，更新当月日历
var year= conYear.value=new Date().getFullYear();
var month= conMonth.value = new Date().getMonth() + 1;
move_day1(year,month);
hide_days(year,month);
move_day30(year,month);

conYear.onchange = conMonth.onchange = function(){
 var year = conYear.value;
 var month = conMonth.value;
 if(year<1900 || year >2100 ){
 year = conYear.value=new Date().getFullYear();
 }
 if(month<1 || month > 12){
 month = conMonth.value=new Date().getMonth() + 1;
 }
 move_day1(year,month);
 hide_days(year,month);
 move_day30(year,month);
}