如何在javascript中获得月和年的第一个日期和最后一个日期

Question

谁能帮我找出月和年的第一次约会和最后一次约会?我有两个参数月和年，例如月= 10，年= 2021

我试了一些代码，但是没有答案

var prevMonthLastDay = new Date(2021, 10, 0);
var thisMonthFirstDay = new Date(2021, 10, 1);
console.log(prevMonthLastDay);
console.log(thisMonthFirstDay);

上面的代码给出如下输出:

2021-10-30T17:00:00.000Z
2021-10-31T17:00:00.000Z 

我期望的答案是第一次约会2021-10-01和最后一次约会2021-10-31

Answer 1

尝试以下操作来获得预期的输出:

function GetFirstAndLastDate(year, month)
{
var firstDayOfMonth = new Date(year, month-1, 2);
var lastDayOfMonth = new Date(year, month, 1);
console.log('First Day: ' + firstDayOfMonth.toISOString().substring(0, 10));
console.log('Last Day: ' + lastDayOfMonth.toISOString().substring(0, 10));
}
GetFirstAndLastDate(2021, 10);

Answer 2

你可以试试这个方法

var date = new Date();
var firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
var lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);

Answer 3

我对你真正想要引用的变量名有点困惑，所以我把它们都包括了:

const currentYear = 2021;
const currentMonth = 10;
const prevMonthFirstDay = new Date(currentYear, currentMonth - 2, 1);
const prevMonthLastDay = new Date(currentYear, currentMonth - 1, 0);
const currentMonthFirstDay = new Date(currentYear, currentMonth - 1, 1);
const currentMonthLastDay = new Date(currentYear, currentMonth, 0);
const nextMonthFirstDay = new Date(currentYear, currentMonth, 1);
const nextMonthLastDay = new Date(currentYear, currentMonth + 1, 0);
console.log('prev month first day:', prevMonthFirstDay);
console.log('prev month last day:', prevMonthLastDay);
console.log('current month first day:', currentMonthFirstDay);
console.log('current month last day:', currentMonthLastDay);
console.log('next month first day:', nextMonthFirstDay);
console.log('next month last day:', nextMonthLastDay);

在我的系统上会给出:

prev month first day: Wed Sep 01 2021 00:00:00 GMT+0700 (Western Indonesia Time)
prev month last day: Thu Sep 30 2021 00:00:00 GMT+0700 (Western Indonesia Time)
current month first day: Fri Oct 01 2021 00:00:00 GMT+0700 (Western Indonesia Time)
current month last day: Sun Oct 31 2021 00:00:00 GMT+0700 (Western Indonesia Time)
next month first day: Mon Nov 01 2021 00:00:00 GMT+0700 (Western Indonesia Time)
next month last day: Tue Nov 30 2021 00:00:00 GMT+0700 (Western Indonesia Time)

所以现在只需要格式化了:

console.log(currentMonthFirstDay.toLocaleDateString('en-GB').split('/').reverse().join('-'));

它会给你:

2021-10-01

Answer 4

你可以这样做。

//first and last of the current month
var current_month = "April 2017";
var arrMonth = current_month.split(" ");
var first_day = new Date(arrMonth[0] + " 1 " + arrMonth[1]);
//even though I already have the values, I'm using date functions to get year and month
//because month is zero-based
var last_day = new Date(first_day.getFullYear(), first_day.getMonth() + 1, 0, 23, 59, 59);
//use moment,js to format       
var start = moment(first_day).format("YYYY-MM-DD");
var end = moment(last_day).format("YYYY-MM-DD");

答案在以下链接中:如何获取月的最后一天

Answer 5

你可以试试这个方法参考

var date = new Date(), y = date.getFullYear(), m = date.getMonth();
var firstDay = new Date(y, m, 1);
var lastDay = new Date(y, m + 1, 0);