日历js代码

//判断闰年
function runNian(_year) {
    if(_year%400 === 0 || (_year%4 === 0 && _year%100 !== 0) ) {
        return true;
    }
    else { return false; }
}
//判断某年某月的1号是星期几
function getFirstDay(_year,_month) {
    var allDay = 0, y = _year-1, i = 1;
    allDay = y + Math.floor(y/4) - Math.floor(y/100) + Math.floor(y/400) + 1;  //公式
    //某年的1月1日星期几的公式   result=(year-1+(year-1)/4-(year-1)/100+(year-1)/400+days)%7;
    // year 是年份，days是当年的天数
    for ( ; i<_month; i++) {
        switch (i) {
            case 1: allDay += 31; break;
            case 2: 
                if(runNian(_year)) { allDay += 29; }
                else { allDay += 28; }
                break;
            case 3: allDay += 31; break;
            case 4: allDay += 30; break;
            case 5: allDay += 31; break;
            case 6: allDay += 30; break;
            case 7: allDay += 31; break;
            case 8: allDay += 31; break;
            case 9: allDay += 30; break;
            case 10: allDay += 31; break;
            case 11: allDay += 30; break;
            case 12: allDay += 31; break;
        }
    }
    return allDay%7;
}
//显示日历
function showCalendar(_year,_month,_day,firstDay) {
    var i = 0,
        monthDay = 0,
        showStr = "",
        _classname = "",
        today = new Date();
        //月份的天数
    switch(_month) {
        case 1: monthDay = 31; break;
        case 2:
            if(runNian(_year)) { monthDay = 29; }
            else { monthDay = 28; }
            break;
        case 3: monthDay = 31; break;
        case 4: monthDay = 30; break;
        case 5: monthDay = 31; break;
        case 6: monthDay = 30; break;
        case 7: monthDay = 31; break;
        case 8: monthDay = 31; break;
        case 9: monthDay = 30; break;
        case 10: monthDay = 31; break;
        case 11: monthDay = 30; break;
        case 12: monthDay = 31; break;
    }

    //输出日历表格，这部分因结构而异
    showStr = "<table class='cld-w'><thead>";
    //日历头部
    showStr += "<tr><th colspan='7'><div class='cld-hd'><span class='cld-pre'>&lt;</span><em id='showDate' value='" + _year + "-" + _month + "-" + _day + "'>" + _year + "年" + _month + "月" + _day + "日" + "</em><span class='cld-next'>&gt;</span></div></th></tr>";
    //日历星期
    showStr += "<tr><th>日</th><th>一</th><th>二</th><th>三</th><th>四</th><th>五</th><th>六</th></tr>";
    showStr += "</thead><tbody><tr>";
    //当月第一天前的空格
    for (i=1; i<=firstDay; i++) {
        showStr += "<td></td>";
    }
    //显示当前月的天数
    for (i=1; i<=monthDay; i++) {
        //当日的日期
        if(_year === today.getFullYear() && _month === today.getMonth()+1 && i === today.getDate()) {
            _classname = "cld-cur"; 
        } 
        //当日之前的日期（这个判断是因为我有工作需求，就是要求之前的日期不能点击）
        else if(_year < today.getFullYear() || (_year === today.getFullYear() && _month <= today.getMonth()) || (_year === today.getFullYear() && _month === today.getMonth()+1 && i < today.getDate()) ) {
            _classname = "cld-old";
        }
        //其他普通的日期
        else { _classname = "cld-day"; }
        //其他大于当月的月份的相同日期（为了让点击下一月的时候，相同的日期增加cld-cur类）
        if(_day === i && (_year > today.getFullYear() || _month > today.getMonth()+1)) { _classname = "cld-cur"; }
        //把日期存在对应的value       
        showStr += "<td class=" + _classname + " value='" + _year + "-" + _month + "-" + i + "'>" + i + "</td>";

        firstDay = (firstDay+1)%7;
        if(firstDay === 0 && i !== monthDay) {
            showStr += "</tr><tr>";
        } 
    }
    
    //剩余的空格
    if(firstDay!==0) {
        for (i=firstDay; i<7; i++) {
            showStr += "<td></td>";
        }
    }
        
    showStr +="</tr></tbody></table>";
    //插入calendar的页面结构里
    calendar.innerHTML = showStr;
}

//显示年月日
function showDate(_year,_month,_day) {
    var date = "", firstDay = getFirstDay(_year,_month,_day);
    if(_day !== 0) {
        date = _year + "年" + _month + "月" +_day + "日";
    }
    else { date = "No Choose."; }
    document.getElementById("showDate").innerHTML = date; //日历头部显示
    showCalendar(_year,_month,_day,firstDay);         //调用日历显示函数
}

//上一月
function preMonth(_year,_month,_day) {
    if(_month == 1) { showDate(_year - 1,12,_day); }
    else { showDate(_year,_month - 1,_day); }
}
//下一月
function nextMonth(_year,_month,_day) {
    if(_month == 12) { showDate(_year + 1,1,_day); }
    else { showDate(_year,_month + 1,_day); }
}
//初始化
var calendar = document.createElement('div');
calendar.setAttribute('id','showCld');
document.getElementById("box").appendChild(calendar); //增加到你的box里

//获取当天的年月日    
var today = new Date();
var _year = today.getFullYear(),
    _month = today.getMonth() + 1,
    _day = today.getDate();
var firstDay = getFirstDay(_year,_month);

//显示日历
showCalendar(_year,_month,_day,firstDay);

//日历点击的事件委托（可以查查js冒泡的应用）
calendar.onclick = function(e) {
    var e = e || window.event;
    var target = e.srcElement || e.target;
//把日历的头部的年月日分割成数组，这里保存在其value属性上
    dayArr = document.getElementById('showDate').getAttribute('value').split('-');
    if (target) {
        //如果是可点击的日期
        if ( target.className === "cld-day" || target.className === "cld-cur" ) {
            dateArr = target.getAttribute('value').split('-');
            //减0是把字符串转化成数值类型，以下一样            
            showDate(dateArr[0]-0,dateArr[1]-0,dateArr[2]-0);
            calendar.className = "";
        } 
        //如果是上一月的点击
        else if ( target.className === "cld-pre" ) {
            preMonth(dayArr[0]-0,dayArr[1]-0,dayArr[2]-0);
        }
        //如果是下一月的点击
        else if ( target.className === "cld-next" ) {
            nextMonth(dayArr[0]-0,dayArr[1]-0,dayArr[2]-0);
        }
    }
};