用javascript添加前導零？

Question

我需要在所有9個月的「下一天」文本框中的月份上添加前導零，並在10,11,12處將其關閉。我不知道如何實現這一點。

幫助！

$(document).ready(function(){ 
 

 
var currentDate = new Date() 
 
    var day = currentDate.getDate() 
 
    if(day <= 9) 
 
    day = '0'+day; 
 
    var month = currentDate.getMonth() + 1 
 
    if(month <= 9) 
 
    month = '0'+month; 
 
    var year = currentDate.getFullYear() 
 
    document.getElementById("element_183").value =("" + month + "/" + day + "/" + year + "") 
 

 
    function DateFromString(str){ 
 
     str = str.split(/\D+/); 
 
     str = new Date(str[2],str[0]-1,(parseInt(str[1])+90)); 
 
     return MMDDYYYY(str); 
 
    } 
 
    
 
    function MMDDYYYY(str) { 
 
     var ndateArr = str.toString().split(' '); 
 
     var Months = 'Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec'; 
 
     return (parseInt(Months.indexOf(ndateArr[+1])/4)+1)+'/'+ndateArr[2]+'/'+ndateArr[3]; 
 
    } 
 

 
    function Add90Days() { 
 
     var date = $('#element_183').val(); 
 
     var ndate = DateFromString(date); 
 
     return ndate; 
 
    } 
 

 
    $('#element_183').ready(function(){ 
 
     $('#element_184').val(Add90Days()); 
 
    }); 
 

 
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script> 
 
Enter date:<input type="text" id="element_183" readonly> 
 
Next date:<input type="text" id="element_184" readonly>

Answer 1

試試下面的代碼：

var currentDate = new Date(); 
 
//currentDate.setMonth(currentDate.getMonth() + 7); 
 
var day = currentDate.getDate() 
 
if(day <= 9) 
 
day = '0'+day; 
 
var month = currentDate.getMonth() + 1 
 
if(month <= 9) 
 
month = '0'+month; 
 
var year = currentDate.getFullYear() 
 
document.getElementById("element_183").value =("" + month + "/" + day + "/" + year + "") 
 

 
function DateFromString(str){ 
 
    str = str.split(/\D+/); 
 
    str = new Date(str[2],str[0]-1,(parseInt(str[1])+90)); 
 
    
 
    return str; 
 
} 
 

 
function MMDDYYYY(str) { 
 
    var ndateArr = str.toString().split(' '); 
 
    var Months = 'Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec'; 
 
    var str = new Date(str); 
 
    
 
    var day = str.getDate(); 
 
    if(day <= 9) 
 
    day = '0'+day; 
 
    var month = str.getMonth() + 1 
 
    if(month <= 9) 
 
    month = '0'+month; 
 
    var year = str.getFullYear() 
 
    return ("" + month + "/" + day + "/" + year + ""); 
 
} 
 

 
function Add90Days() { 
 
    var date = $('#element_183').val(); 
 
    var ndate = MMDDYYYY(DateFromString(date)); 
 
    return ndate; 
 
} 
 

 
$('#element_183').ready(function(){ 
 
    $('#element_184').val(Add90Days()); 
 
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> 
 
Enter date:<input type="text" id="element_183" readonly> 
 
Next date:<input type="text" id="element_184" readonly>

Answer 2

我將使用this answer使用的技術，這樣的榮譽給該用戶。

var currentDate = new Date('01/15/2017'); 
var currentDay = ('0' + currentDate.getDate()).slice(-2); 
var currentMonth = ('0' + (currentDate.getMonth() + 1)).slice(-2); 
// This is not just relevant to dates! 
var number = 3; 
var paddedNumber = ('0' + number).slice(-2); 

// currentDay = '15' 
// currentMonth = '01' 
// number = '03' 

.slice(-2)做什麼是執行一個「串」，但是從字符串的末尾開始，切斷前面。這樣，如果您已經有2位數的日期或月份，它會變成3個字符，那麼第一個將被刪除。

Answer 3

我一直在測試這個問題，我明白了這樣的工作：

$(document).ready(function(){ 

var currentDate = new Date() 
    var day = currentDate.getDate() 
    if(day <= 9) 
    var stringDay = '0'+day.toString(); 
    var month = currentDate.getMonth() + 1 
    if(month <= 9) 
    var stringMonth = '0'+month.toString(); 
    var year = currentDate.getFullYear() 
    document.getElementById("element_183").value =("" + stringMonth + "/" + stringDay + "/" + year + "") 

    function DateFromString(str){ 
     str = str.split(/\D+/); 
     str = new Date(str[2],str[0]-1,(parseInt(str[1])+90)); 
     return MMDDYYYY(str); 
    } 

    function MMDDYYYY(str) { 
     var ndateArr = str.toString().split(' '); 
     var Months = 'Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec'; 
     return (parseInt(Months.indexOf(ndateArr[+1])/4)+1)+'/'+ndateArr[2]+'/'+ndateArr[3]; 
    } 

    function Add90Days() { 
     var date = $('#element_183').val(); 
     var ndate = DateFromString(date); 
     return ndate; 
    } 

    $('#element_183').ready(function(){ 
     $('#element_184').val(Add90Days()); 
    }); 

}); 

我希望這是你想要的:)

問候，