JavaScript 实现简易日历组件的开发逻辑与代码解析

完整代码实现与结构解析

<!doctype html>
<html lang="en">
 <head>
 <meta charset="UTF-8">
 <meta name="Generator" content="EditPlus®">
 <meta name="Author" content="">
 <meta name="Keywords" content="">
 <meta name="Description" content="">
 <title>calendar</title>
 <style>
 .clear:after{
 content:"";
 display:table;
 clear:both;
 }
 .left{
 float:left;
 }
 ul{
 padding:0px;
 margin-top:5px;
 margin-bottom:0px;
 }
 ul>li{
 float:left;
 list-style:none;
 width:30px;
 height: 21px;
 border: 1px solid #ccc;
 text-align:center;
 }
 .gray{
 color:#766565;
 }
 .top {
 height:25px;
 }
 .top .lf-tri{
 border:10px solid transparent;
 border-right-color:black;
 margin-top:4px;
 }
 .top .rf-tri{
 border:10px solid transparent;
 border-left-color:black;
 margin-top:4px;
 }
 .top .content{
 width:185px;
 height:5px;
 text-align:center;
 }
 </style>
 </head>
 <body> 
 <div class="top clear">
 <div class="left lf-tri" onclick="lastMonth()"></div>
 <div class="left content">2017年2月1日</div>
 <div class="left rf-tri" onclick=" nextMonth()"></div>
 </div>
 <div>
 <div id="week">
 <ul class="clear">
 <li>日</li>
 <li>一</li>
 <li>二</li>
 <li>三</li>
 <li>四</li>
 <li>五</li>
 <li>六</li>
 <ul>
 </div>
 <div id="date" onclick='getDateNum(event)'>
 <ul class="clear">
 <li>30</li>
 <li>31</li>
 <li>1</li>
 <li>2</li>
 <li>3</li>
 <li>4</li>
 <li>5</li>
 </ul>
 <ul class="clear">
 <li>6</li>
 <li>7</li>
 <li>8</li>
 <li>9</li>
 <li>10</li>
 <li>11</li>
 <li>12</li>
 </ul>
 <ul class="clear">
 <li>13</li>
 <li>14</li>
 <li>15</li>
 <li>16</li>
 <li>17</li>
 <li>18</li>
 <li>19</li>
 </ul>
 <ul class="clear">
 <li>20</li>
 <li>21</li>
 <li>22</li>
 <li>23</li>
 <li>24</li>
 <li>25</li>
 <li>26</li>
 </ul>
 <ul class="clear">
 <li>27</li>
 <li>28</li>
 <li>1</li>
 <li>2</li>
 <li>3</li>
 <li>4</li>
 <li>5</li>
 </ul>
 <ul class="clear">
 <li>27</li>
 <li>28</li>
 <li>1</li>
 <li>2</li>
 <li>3</li>
 <li>4</li>
 <li>5</li>
 </ul>
 </div>
 <div>
 <script>
 function $(id){
 return document.getElementById(id);
 }
 function change(cls){
 return document.getElementsByClassName(cls);
 }
 function getDateNum(e) {
 console.log(e && e.target.nodeName)//打印发生事件的元素，再获取元素nodeName
 if(e.target.nodeName=="LI"){//先判断nodeName是LI
 if(e.target.className!="gray"){//点击本月的日期，显示在日期栏
 change("content")[0].innerHTML = year+'年'+(month+1)+'月'+e.target.innerHTML+'日';
 }else{//点击灰色日期即（上个月或者下个月日期）切换到当月
 if(e.target.innerHTML>14){
 lastMonth();
 }else {
 nextMonth();
 }
 }
 }
 }
 //获取年、月
 var today = new Date();
 var year=today.getFullYear(), month = today.getMonth();
 var totalDay;
 var uls=$("date").children,list;
 function loadCalendar(){
 totalDay=getMonthDays(year,month+1);//计算一个月的天数
 var firstDay = (new Date(year,month,1)).getDay();//计算每个月1号在星期几
 var lastMonthDay=getMonthDays(year,month);
 var lastDayCal=lastMonthDay-firstDay+1;//计算上个月在第一行显示的天数
 //获取ul元素
 var num=1 ,nextNum=1;//日期显示
 // 类数组对象 转 数组
 //uls = Array.prototype.slice.call(uls)
 //获取li元素 填充
 for(var r=0;r<uls.length;r++){
 list=uls[r].children;//遍历ul,获得li
 for(var line=0;line<list.length;line++){
 if(r==0){//在第一行 与第一天进行判断 大于等于第一天时载入日期
 if(line>=firstDay){
 list[line].innerHTML=num++;
 list[line].setAttribute("class","");
 }else {
 list[line].innerHTML=lastDayCal++;//第一行的上个月天数显示
 list[line].setAttribute("class","gray");
 }
 }else {
 //判断是否超出天数 ,不超出则继续加，超出则显示下个月日期
 if(num<=totalDay){
 list[line].setAttribute("class","");
 list[line].innerHTML=num++;
 }else {
 list[line].innerHTML=nextNum++;//下个月日期显示
 list[line].setAttribute("class","gray");
 }
 }
 }
 }
 }
 loadCalendar();
 function getMonthDays(year,month){
 //判断2月份天数
 if(month==2){
 days= (year%4==0)&&(year%100!=0)||(year%400==0)? 29:28;
 }else {
 //1-7月 单数月为31日 
 if(month<7){
 days= month%2==1?31:30;
 }else {
 //8-12月 双月为31日
 days = month%2==0?31:30;
 }
 }
 return days; 
 }
 //右击箭头下个月
 //change("rf-tri")[0].onclick =
 function nextMonth() {
 month++;
 if(month>11){
 year+=1;
 month=0;
 }
 change("content")[0].innerHTML=year+"年"+(month+1)+"月"+"1日";
 //console.log(month+1);
 loadCalendar();
 }
 //左击箭头上个月
 //change("lf-tri")[0].onclick =
 function lastMonth() {
 month--;
 if(month<0){
 month=11;
 year-=1;
 }
 change("content")[0].innerHTML=year+"年"+(month+1)+"月"+"1日";
 //console.log(month+1);
 loadCalendar();
 }
 </script>
 </body>
</html>