日期对象算法，用于返回最接近的每两周一天的日期

Date Object algorithm to return date of nearest bi-weekly day of week

本文关键字：日期 两周 一天 最接近 返回 对象 算法 用于      更新时间：2023-09-26

目标：自动显示即将举行的双周活动的日期。在这种情况下，每个星期六。理想情况下，通过修改现有代码。

例如，如果 7 月 9 日有一个事件，而今天是 7 月 11 日，则下一个事件将是 7 月 23 日。如果今天是 7 月 24 日，下一个事件是 8 月 6 日，依此类推......

问题：如何计算日期？（我假设需要一个参考开始日期，例如 2016 年 7 月 9 日）

背景/现有代码：计算一周中最近的给定日期。（例如，如果今天是 14 日星期一，那么即将到来的星期六的日期是什么？注意：在这种情况下，活动是每周五和周六。我们显示即将到来的周五和周六的日期。但我想确保显示的日期总是在同一个周末。（如果今天是星期六，FRI 日期应该是昨天，SAT 日期应该是今天）。

(function() {
  // Today's date
  var startingDate = new Date();
  // Find date of nearest day of week
  function dateOfNearestDay(startingDate, nearestDay) {
    // Date object to work with inside the function
    var nearestTime = new Date(startingDate.getTime());
    // If today is Sat, use last Fri's date, else calculate date of nearest day
    if (startingDate.getDay() === 6 && nearestDay === 5) {
      nearestTime.setDate((startingDate.getDate() + (7 + nearestDay - startingDate.getDay()) % 7) - 7);
    } 
    else {
      nearestTime.setDate(startingDate.getDate() + (7 + nearestDay - startingDate.getDay()) % 7);
    }
    return nearestTime;
  }
  // Format date as needed for display
  function getMonthAndDay(date) {
    // Array to store month names for translation
    monthNames = ['Jan.', 'Feb.', 'Mar.', 'Apr.', 'May', 'Jun.', 'Jul.', 'Aug.', 'Sep.', 'Oct.', 'Nov.', 'Dec.'];
    return monthNames[date.getMonth()]+ " " + date.getDate();
  }
  // Get date object of nearest Friday and Saturday
  var friday = dateOfNearestDay(startingDate, 5);
  var saturday = dateOfNearestDay(startingDate, 6);
  var fridayDate = document.getElementById('friday');
  var saturdayDate = document.getElementById('saturday');
  // Write month & day of nearest day
  fridayDate.textContent = getMonthAndDay(friday);    
  saturdayDate.textContent = getMonthAndDay(saturday);
}());

event的给定日期today和已知日期的函数nextEvent计算today或today后的下一个双周重复事件：

// Today's date
var startingDate = new Date();
startingDate.setDate(startingDate.getDate());
// Find date of nearest day of week
function dateOfNearestDay(startingDate, nearestDay) {
    // Date object to work with inside the function
    var nearestTime = new Date(startingDate.getTime());
    // If today is Sat, use last Fri's date, else calculate date of nearest day
    if (startingDate.getDay() === 6 && nearestDay === 5) {
      nearestTime.setDate((startingDate.getDate() + (7 + nearestDay - startingDate.getDay()) % 7) - 7 - 7);
    } else {
      nearestTime.setDate(startingDate.getDate() + (7 + nearestDay - startingDate.getDay()) % 7 - 7);
    }
    return nearestTime;
}
// For a given today and last event finds closest next event from today.
// Assumption is that event is recurring every 14 days
function nextEvent(today, event) {
    var eventRecurrence = 14; // recurrence of the event in days
    var nextEventTime = new Date(today.getTime());
    nextEventTime.setDate(today.getDate() + ((today.getDate() > event.getDate()) ? eventRecurrence : 0) - (today.getDate() - event.getDate()) % eventRecurrence);
    return nextEventTime;
}
// Format date as needed for display
function getMonthAndDay(date) {
    // Array to store month names for translation
    monthNames = ['Jan.', 'Feb.', 'Mar.', 'Apr.', 'May', 'Jun.', 'Jul.', 'Aug.', 'Sep.', 'Oct.', 'Nov.', 'Dec.'];
    return monthNames[date.getMonth()] + " " + date.getDate();
}
// Get date object of nearest Friday and Saturday
var friday = dateOfNearestDay(startingDate, 5);
var saturday = dateOfNearestDay(startingDate, 6);
var nextFridayEvent = nextEvent(startingDate, friday);
var nextSaturdayEvent = nextEvent(startingDate, saturday);
// Write months & days of the variables
console.log('Today is ' + getMonthAndDay(startingDate));
console.log('Friday Event ' + getMonthAndDay(friday));
console.log('Saturday Event ' + getMonthAndDay(saturday));
console.log('Next Friday Event ' + getMonthAndDay(nextFridayEvent));
console.log('Next Saturday Event ' + getMonthAndDay(nextSaturdayEvent))

我已经用 2x -7修改了您的函数dateOfNearestDay，以便在today之前演示事件。

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