首页 \ 问答 \ 创建局部变量以在javascript中跟踪日历上的月份。(Creating a local variable to keep track of months on a calendar in javascript.)

创建局部变量以在javascript中跟踪日历上的月份。(Creating a local variable to keep track of months on a calendar in javascript.)

 在这里，我有一个完整的html页面，用于创建日历，复制它以查看它的作用。 我下面有两个按钮可以逐个增加。 我的问题是因为我可以在页面顶部实例化var month= date.getMonth() ，全局变量month只允许我递增1，我怎么能让month设置为局部变量所以我是能够增加到超过1.这是代码：我确信复制粘贴将工作：  
 下面我发布了我的按钮处理程序以增加月份/减少月份。  
<script type="text/javascript"> 

printCalendar(year,month,divDestination);
function printCalendar(year,mth,divDestination){
var currentmonth = mth;
var myOutput=document.getElementById(divDestination)
myOutput.innerHTML=makeCalendar(year,mth)
}
function prevMonth(m){
    m--;
    var currentmonth = m;
    alert(m);
    if(m < 0)
    {
        m = 11;
        year--;
    }

    printCalendar(year,currentmonth,divDestination);
}
function nextMonth(m){
    m++;    
    var currentmonth = m;
    if(m > 11)
    {
        m=0;
        year++;
    }
    printCalendar(year,currentmonth,divDestination);
}
function test(div){
var myOutput=document.getElementById("divCalendar")
myOutput.innerHTML += eventmonth;
}
</script>

<div align="center" id="divCalendar"></div>
<div align="center" id="myButtons">
<input type="button" onclick="test('divCalendar')" value="Say hi" />
<input type="button" onclick="prevMonth(month,'divCalendar')" value="Previous"/>
<input type="button" onclick="nextMonth(month,'divCalendar')" value="Next" />
<input type="button" onclick="printCalendar(year,month,'divCalendar')" value="Reload Calendar" />
 
 下面是我的makeCalendar函数  
var myDate = new Date();
    var month = myDate.getMonth();
    var year = myDate.getFullYear();
    var divDestination="divCalendar";

    function leapYear(yr) { 
        if (yr < 1000) yr+=1900
        return((yr%4 == 0) && ((yr%100 == 0) || (yr%400 ==0)))
    }

    function startCol(width, height, color){
        return('<TD WIDTH=' + width + ' HEIGHT=' + height + '>' + '<FONT COLOR="' + color + '">');
    }

    function getHoliday(monthSelected,theday)
    {
        monthSelected = monthSelected + 1
        var holiday = ""
        var HolidayName = new Array (1, 1, "New Year's Day",7, 1, "Canada Day",12, 25, "Christmas Day",12, 26, "Boxing Day", 2,14,"Valentine's Day")
        for(var index = 0; HolidayName.length >= index; index++)
        {   
            if(HolidayName[index] == monthSelected && HolidayName[index+1] == theday)
            {
                holiday = HolidayName[index+2]
            }
        }
        return holiday
    }

    function makeCalendar(yr, mth)
    {
        var monthSelected = mth
        var months    = new Array("Jan", "Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec")
        var days      = new Array(31, leapYear(yr)?29:28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
        var weekDays  = new Array("Sun", "Mon", "Tues", "Wed", "Thurs", "Fri", "Sat")

        var mthSz         = days[mth]
        var mthName       = months[mth]
        var firstDyofMnth = new Date(yr, mth, 1)
        var firstDay      = firstDyofMnth.getDay() + 1
        var numRows       = Math.ceil((mthSz + firstDay-1)/7)
        var mthNameHeight = 50

        var borderWidth   = 2
        var cellSpacing   = 4 
        var cellHeight    = 80 

        var hdrColor      = "midnightblue" 
        var hdrSz         = "+3" 
        var colWidth      = 100 

        var dayCellHeight = 25 
        var dayColor      = "black" 
        var dayCtr        = 1

        // Build the HTML Table 
        var txt = '<CENTER>'
        txt += '<TABLE BORDER=' + borderWidth + ' CELLSPACING=' + cellSpacing + '>' 

        //Show Month Name and Year
        txt += '<TH COLSPAN=7 HEIGHT=' + mthNameHeight + '>' 
        txt += '<FONT COLOR="' + hdrColor + '" SIZE=' + hdrSz + '>' 
        txt += mthName + ' ' + year + '</FONT>' + '</TH>'

        // Show Days of the Week 
        txt += '<TR ALIGN="center" VALIGN="center">'
        for (var dy = 0; dy < 7; ++dy) {
            txt += startCol(colWidth, dayCellHeight, dayColor) + weekDays[dy] + '</FONT></TD>' 
        }
        txt += '</TR>'

        // Show Dates in Calendar
        for (var row=1; row <= numRows; ++row) 
        {
            txt += '<TR ALIGN="right" VALIGN="top">'
            for (var col = 1; col <= 7; ++col) 
            {
                if (((col < firstDay) && (row==1)) || (dayCtr>mthSz))
                    {txt += '<TD BGCOLOR="Gainsboro"><BR></TD>'}
                else
                    {
                        var event = getHoliday(monthSelected, dayCtr)
                        txt += '<TD HEIGHT=' + cellHeight + '><FONT COLOR="' + dayColor + '"> <B>'
                        txt += dayCtr
                        txt += '</B></FONT><BR>' + event + '</TD>'
                        dayCtr++;
                    }       
            }
            txt += '</TR>'
        }
        // close all basic table tags and output txt string
        txt += '</TABLE></CENTER>'  
        return txt
        }

Here I have below a full html page for a calendar creation, copy it over to see what it does. I have two buttons below that can increment month by one. My problem is because I can instantiating var month= date.getMonth() at the top of the page, the global variable month only allows me to increment and decrement by 1, how can I let month be set as a local variable so I am able to increment to more than just 1. Here is the code: I'm sure copy paste will work: 
Below I have posted my my button handlers to increase month/decrease month.  
<script type="text/javascript"> 

printCalendar(year,month,divDestination);
function printCalendar(year,mth,divDestination){
var currentmonth = mth;
var myOutput=document.getElementById(divDestination)
myOutput.innerHTML=makeCalendar(year,mth)
}
function prevMonth(m){
    m--;
    var currentmonth = m;
    alert(m);
    if(m < 0)
    {
        m = 11;
        year--;
    }

    printCalendar(year,currentmonth,divDestination);
}
function nextMonth(m){
    m++;    
    var currentmonth = m;
    if(m > 11)
    {
        m=0;
        year++;
    }
    printCalendar(year,currentmonth,divDestination);
}
function test(div){
var myOutput=document.getElementById("divCalendar")
myOutput.innerHTML += eventmonth;
}
</script>

<div align="center" id="divCalendar"></div>
<div align="center" id="myButtons">
<input type="button" onclick="test('divCalendar')" value="Say hi" />
<input type="button" onclick="prevMonth(month,'divCalendar')" value="Previous"/>
<input type="button" onclick="nextMonth(month,'divCalendar')" value="Next" />
<input type="button" onclick="printCalendar(year,month,'divCalendar')" value="Reload Calendar" />
 
Here below is my makeCalendar function 
var myDate = new Date();
    var month = myDate.getMonth();
    var year = myDate.getFullYear();
    var divDestination="divCalendar";

    function leapYear(yr) { 
        if (yr < 1000) yr+=1900
        return((yr%4 == 0) && ((yr%100 == 0) || (yr%400 ==0)))
    }

    function startCol(width, height, color){
        return('<TD WIDTH=' + width + ' HEIGHT=' + height + '>' + '<FONT COLOR="' + color + '">');
    }

    function getHoliday(monthSelected,theday)
    {
        monthSelected = monthSelected + 1
        var holiday = ""
        var HolidayName = new Array (1, 1, "New Year's Day",7, 1, "Canada Day",12, 25, "Christmas Day",12, 26, "Boxing Day", 2,14,"Valentine's Day")
        for(var index = 0; HolidayName.length >= index; index++)
        {   
            if(HolidayName[index] == monthSelected && HolidayName[index+1] == theday)
            {
                holiday = HolidayName[index+2]
            }
        }
        return holiday
    }

    function makeCalendar(yr, mth)
    {
        var monthSelected = mth
        var months    = new Array("Jan", "Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec")
        var days      = new Array(31, leapYear(yr)?29:28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
        var weekDays  = new Array("Sun", "Mon", "Tues", "Wed", "Thurs", "Fri", "Sat")

        var mthSz         = days[mth]
        var mthName       = months[mth]
        var firstDyofMnth = new Date(yr, mth, 1)
        var firstDay      = firstDyofMnth.getDay() + 1
        var numRows       = Math.ceil((mthSz + firstDay-1)/7)
        var mthNameHeight = 50

        var borderWidth   = 2
        var cellSpacing   = 4 
        var cellHeight    = 80 

        var hdrColor      = "midnightblue" 
        var hdrSz         = "+3" 
        var colWidth      = 100 

        var dayCellHeight = 25 
        var dayColor      = "black" 
        var dayCtr        = 1

        // Build the HTML Table 
        var txt = '<CENTER>'
        txt += '<TABLE BORDER=' + borderWidth + ' CELLSPACING=' + cellSpacing + '>' 

        //Show Month Name and Year
        txt += '<TH COLSPAN=7 HEIGHT=' + mthNameHeight + '>' 
        txt += '<FONT COLOR="' + hdrColor + '" SIZE=' + hdrSz + '>' 
        txt += mthName + ' ' + year + '</FONT>' + '</TH>'

        // Show Days of the Week 
        txt += '<TR ALIGN="center" VALIGN="center">'
        for (var dy = 0; dy < 7; ++dy) {
            txt += startCol(colWidth, dayCellHeight, dayColor) + weekDays[dy] + '</FONT></TD>' 
        }
        txt += '</TR>'

        // Show Dates in Calendar
        for (var row=1; row <= numRows; ++row) 
        {
            txt += '<TR ALIGN="right" VALIGN="top">'
            for (var col = 1; col <= 7; ++col) 
            {
                if (((col < firstDay) && (row==1)) || (dayCtr>mthSz))
                    {txt += '<TD BGCOLOR="Gainsboro"><BR></TD>'}
                else
                    {
                        var event = getHoliday(monthSelected, dayCtr)
                        txt += '<TD HEIGHT=' + cellHeight + '><FONT COLOR="' + dayColor + '"> <B>'
                        txt += dayCtr
                        txt += '</B></FONT><BR>' + event + '</TD>'
                        dayCtr++;
                    }       
            }
            txt += '</TR>'
        }
        // close all basic table tags and output txt string
        txt += '</TABLE></CENTER>'  
        return txt
        }

原文：https://stackoverflow.com/questions/14883674

更新时间：2022-07-27 10:07

最满意答案

 每列存储一个值，否则您无法进行关系查询。 有关数据库规范化的介绍，请参阅此优秀讨论 。  
 users  
uid
...
 
 followers  
uid u_follow
1   2
1   3
2   1
2   3
3   1
3   2
5   2
5   3
5   4
 
 然后：  
select u_follow, count(*) as num_followers from followers group by u_follow
 
 如果您想要包含没有关注者的用户，请执行以下操作：  
with a as (
  select u_follow, count(*) as num_followers
  from followers group by u_follow
)
select users.uid, coalesce(a.num_followers,0)
from users outer join a on users.uid = a.u_follow

Store one value per column, otherwise you just can't do relational queries. See this excellent discussion for an introduction to database normalization. 
users 
uid
...
 
followers 
uid u_follow
1   2
1   3
2   1
2   3
3   1
3   2
5   2
5   3
5   4
 
Then: 
select u_follow, count(*) as num_followers from followers group by u_follow
 
If you want to include users with no followers do something like: 
with a as (
  select u_follow, count(*) as num_followers
  from followers group by u_follow
)
select users.uid, coalesce(a.num_followers,0)
from users outer join a on users.uid = a.u_follow

创建局部变量以在javascript中跟踪日历上的月份。(Creating a local variable to keep track of months on a calendar in javascript.)

最满意答案

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