Javascript 分别选择字符

我只需要选择天、月和年（分别），然后计算到期日。为什么它不能正常工作？我是否正确使用了

substr

你能试试这个吗

var monthDue = $('.due-date').text().substr(0,2);
var dayDue = $('.due-date').text().substr(3,2);
var yearDue = $('.due-date').text().substr(6,4);

我还建议您查看moment.js，了解日期操作或计算。

$（此）

不是您所认为的，请尝试以下方法：

/* caching the relevant text to avoid having to find the same element/text
   multiple times: */
var due = $('.due-date').text(),
    monthDue = due.substr(0,2),
    dayDue = due.substr(3,2),
    yearDue = due.substr(6,4);

// to demonstrate that you're getting the relevant text
console.log(yearDue, monthDue, dayDue);

$('.days-due').each(function(){
    $(this).text(daysUntil(yearDue, monthDue, dayDue));
});

.

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标签数学是什么？？

/* caching the relevant text to avoid having to find the same element/text
   multiple times: */
var due = $('.due-date').text(),
    monthDue = due.substr(0,2),
    dayDue = due.substr(3,2),
    yearDue = due.substr(6,4);

// to demonstrate that you're getting the relevant text
console.log(yearDue, monthDue, dayDue);

$('.days-due').each(function(){
    $(this).text(daysUntil(yearDue, monthDue, dayDue));
});

function daysUntil(untilDate) {
    var Time = new Date(untilDate).getTime();
    var currTime = new Date().getTime();
    var difference = Time-currTime; 
    return Math.ceil( difference/(1000*60*60*24) );   
}


$('.days-due').each(function() {
    var dateUntil = $('.due-date').text(); // use something more specific
    $(this).text( daysUntil( dateUntil ) );
} );