用 JavaScript 计算上周开始日期（不是 -7 天前）

Question

我有一个活动记录列表，它们都有日期并显示在活动流中。

我想根据记录的创建日期在记录之间插入分隔符 DIV。

我想显示一个带有文本 本周 的 DIV，它将采用当前一周的开始日期（不超过 7 天），然后我可以显示自该日期以来创建的所有记录。

我还想为 上周 做一个，这意味着我需要获取上周开始日期和上周结束日期的 Date 值。或者开始日期 +7 就可以了。

然后我有一个 JavaScript 库来比较日期范围。我可以传入开始日期和结束日期，并确定第三个日期是否在日期范围内，这将使我知道在每个日期部分下显示哪些记录。

所以我请求帮助计算：

一周的开始日期是大多数日历中的星期日或星期一

• 当前周开始日期
• 上周开始日期和结束日期

此外，如果我能提供帮助，我不希望将庞大的 Moment.js 库用于这些少数日期操作。

感谢您的帮助

下图显示了我试图通过日期部分来打破我的记录...

---

用于 DateTime 比较和检查日期是否在 2 个日期范围之间的日期库！

// Source: http://stackoverflow.com/questions/497790
var dates = {
  convert: function(d) {
    // Converts the date in d to a date-object. The input can be:
    //   a date object: returned without modification
    //  an array      : Interpreted as [year,month,day]. NOTE: month is 0-11.
    //   a number     : Interpreted as number of milliseconds
    //                  since 1 Jan 1970 (a timestamp)
    //   a string     : Any format supported by the javascript engine, like
    //                  "YYYY/MM/DD", "MM/DD/YYYY", "Jan 31 2009" etc.
    //  an object     : Interpreted as an object with year, month and date
    //                  attributes.  **NOTE** month is 0-11.
    return (
      d.constructor === Date ? d :
      d.constructor === Array ? new Date(d[0], d[1], d[2]) :
      d.constructor === Number ? new Date(d) :
      d.constructor === String ? new Date(d) :
      typeof d === "object" ? new Date(d.year, d.month, d.date) :
      NaN
    );
  },
  compare: function(a, b) {
    // Compare two dates (could be of any type supported by the convert
    // function above) and returns:
    //  -1 : if a < b
    //   0 : if a = b
    //   1 : if a > b
    // NaN : if a or b is an illegal date
    // NOTE: The code inside isFinite does an assignment (=).
    return (
      isFinite(a = this.convert(a).valueOf()) &&
      isFinite(b = this.convert(b).valueOf()) ?
      (a > b) - (a < b) :
      NaN
    );
  },
  inRange: function(d, start, end) {
    // Checks if date in d is between dates in start and end.
    // Returns a boolean or NaN:
    //    true  : if d is between start and end (inclusive)
    //    false : if d is before start or after end
    //    NaN   : if one or more of the dates is illegal.
    // NOTE: The code inside isFinite does an assignment (=).
    return (
      isFinite(d = this.convert(d).valueOf()) &&
      isFinite(start = this.convert(start).valueOf()) &&
      isFinite(end = this.convert(end).valueOf()) ?
      start <= d && d <= end :
      NaN
    );
  },

  // Subtract number of months from current month
  // dates.subtractMonth(1)
  subtractMonth: function(numberOfMonths) {
    //var d = this;
    var d = new Date();
    d.setMonth(d.getMonth() - numberOfMonths);
    d.setDate(1);
    return d;
  }

};

///////////////////////////////////////////////////////////////////////////

我的示例 JSON 数据的日期将与其他日期进行比较以确定何时将日期部分标题注入循环

var task_activities = [{"id":1,"name":"record 1","date_time":"1\/5\/2015"},{"id":2,"name":"record 2","date_time":"1\/9\/2015"},{"id":3,"name":"record 3","date_time":"1\/13\/2015"},{"id":4,"name":"record 4","date_time":"1\/17\/2015"},{"id":5,"name":"record 5","date_time":"1\/21\/2015"},{"id":6,"name":"record 6","date_time":"1\/25\/2015"},{"id":7,"name":"record 7","date_time":"1\/29\/2015"},{"id":8,"name":"record 8","date_time":"2\/1\/2015"},{"id":9,"name":"record 9","date_time":"2\/5\/2015"},{"id":10,"name":"record 10","date_time":"2\/9\/2015"},{"id":11,"name":"record 11","date_time":"2\/13\/2015"},{"id":12,"name":"record 12","date_time":"2\/17\/2015"},{"id":13,"name":"record 13","date_time":"2\/21\/2015"},{"id":14,"name":"record 14","date_time":"2\/25\/2015"},{"id":15,"name":"record 15","date_time":"2\/29\/2015"},{"id":16,"name":"record 16","date_time":"3\/1\/2015"},{"id":17,"name":"record 17","date_time":"3\/5\/2015"},{"id":18,"name":"record 18","date_time":"3\/9\/2015"},{"id":19,"name":"record 19","date_time":"3\/13\/2015"},{"id":20,"name":"record 20","date_time":"3\/17\/2015"}];



// Loop over each Task Activity record and generate HTML
$.each(task_activities, function(i, activity) {
    console.log(activity.date_time);
}); // end each

Answer 1

首先，subtractMonth 函数存在缺陷，3 月 31 日减去 1 个月返回 3 月 1 日。

如果您想找到给定日期一周的第一天，只需从星期天开始的星期的日期中减去天数，或者从星期一开始的星期减去星期天或星期天减去 6 天：

/**
**  @param {Date} date - date to get start of week for
**  @param {Boolean} mondayStart - falsey for Sunday as first day of week,
**                                 truthy for Monday as first day of week
**  @returns {Date} - date for first day of week
*/
function getStartOfWeek(date, mondayStart) {

  // copy date
  var d = new Date(+date);
  // days to previous Sunday
  var shift = d.getDay();

  // Adjust shift if week starts on Monday
  if (mondayStart) {
    shift = shift? shift - 1 : 6;
  }

  // Shift to start of week
  d.setDate(d.getDate() - shift);
  return d;
}

如果您希望 subtractMonth 函数起作用，请说出您希望它做什么。

编辑

作为一项奖励功能，这里有一个减月功能，我认为它的工作原理是这样的：

/*
** @param {number} numberOfMonths - number of months to add to date
** @param {Date} date - date to subract months from
** @returns {Date} - the passed in date object with the specified number of months subtracted
*/
function subtractMonth (numberOfMonths, date) {

  // If date not supplied, default to today
  var d = date || new Date();

  // Get the date
  var day = d.getDate();

  // Subtract the months
  d.setMonth(d.getMonth() - numberOfMonths);

  // If date has changed, was too big for month and has rolled over
  // into next month, so set to last day of previous month
  if (day != d.getDate) d.setDate(0);
  return d;
}