代码之家 › 专栏 › 技术社区 › Kraang Prime

在没有附加库的情况下使用JavaScript获取当前一周[所以例子都是错误的]

date javascript

-1

Kraang Prime · 技术社区 · 7 年前

我构建了一个日历控件,并添加了周数作为最后一步,但在SO上和SO之外找到的每个脚本示例都遇到了问题(其中大部分都是从另一个脚本复制的)。

下面是其中一个库的可视化演示(它们都有其不精确之处,因为它们通常是根据固定的数字计算一周,然后从那里构建):

您可以查看 codepen here 由于项目相当复杂,我有 Date.prototype.getWeek 功能一开始就玩起来容易些。您可以随意交换这里找到的示例中的任何代码,因为它们最终都会在几个月内出现问题。

当运行“Get week of year in JavaScript like in PHP”中的最新示例(2017)时,现在返回的周数是42。当您查看我的日历时,现在10月份的周数显示为42,根据这里的说明,这是正确的 https://www.epochconverter.com/weeks/2018 .

举个例子,有整整一周的时间共享同一周的数字-所以我不知道怎么做 42 甚至可以是准确的。

Date.prototype.getWeek = function (dowOffset) {
/*getWeek() was developed by Nick Baicoianu at MeanFreePath: http://www.epoch-calendar.com */

    dowOffset = typeof(dowOffset) == 'int' ? dowOffset : 0; //default dowOffset to zero
    var newYear = new Date(this.getFullYear(),0,1);
    var day = newYear.getDay() - dowOffset; //the day of week the year begins on
    day = (day >= 0 ? day : day + 7);
    var daynum = Math.floor((this.getTime() - newYear.getTime() - 
    (this.getTimezoneOffset()-newYear.getTimezoneOffset())*60000)/86400000) + 1;
    var weeknum;
    //if the year starts before the middle of a week
    if(day < 4) {
        weeknum = Math.floor((daynum+day-1)/7) + 1;
        if(weeknum > 52) {
            nYear = new Date(this.getFullYear() + 1,0,1);
            nday = nYear.getDay() - dowOffset;
            nday = nday >= 0 ? nday : nday + 7;
            /*if the next year starts before the middle of
              the week, it is week #1 of that year*/
            weeknum = nday < 4 ? 1 : 53;
        }
    }
    else {
        weeknum = Math.floor((daynum+day-1)/7);
    }
    return weeknum;
};

Here is some code (也尝试了这个)这是星期天特定的(见底部附近)。我还在这里贴上了相关的剪贴画:

/* For a given date, get the ISO week number
 *
 * Based on information at:
 *
 *    http://www.merlyn.demon.co.uk/weekcalc.htm#WNR
 *
 * Algorithm is to find nearest thursday, it's year
 * is the year of the week number. Then get weeks
 * between that date and the first day of that year.
 *
 * Note that dates in one year can be weeks of previous
 * or next year, overlap is up to 3 days.
 *
 * e.g. 2014/12/29 is Monday in week  1 of 2015
 *      2012/1/1   is Sunday in week 52 of 2011
 */
function getWeekNumber(d) {
    // Copy date so don't modify original
    d = new Date(Date.UTC(d.getFullYear(), d.getMonth(), d.getDate()));
    // Set to nearest Thursday: current date + 4 - current day number
    // Make Sunday's day number 7
    d.setUTCDate(d.getUTCDate() + 4 - (d.getUTCDay()||7));
    // Get first day of year
    var yearStart = new Date(Date.UTC(d.getUTCFullYear(),0,1));
    // Calculate full weeks to nearest Thursday
    var weekNo = Math.ceil(( ( (d - yearStart) / 86400000) + 1)/7);
    // Return array of year and week number
    return [d.getUTCFullYear(), weekNo];
}

1 回复 | 直到 7 年前

RobG 7 年前

算法是使用下一个星期六的周数。所以在下一个星期六,然后用它作为1月1日的年份。如果不是星期天,就转到上一个星期天。然后得到从那里开始的周数。听起来可能有点复杂,但这只是几行代码。以下大部分是游戏的助手。

希望评论足够了, 返回 [year, weekNumber]

/* Get week number in year based on:
 *  - week starts on Sunday
 *  - week number and year is that of the next Saturday,
 *    or current date if it's Saturday
 *    1st week of 2011 starts on Sunday 26 December, 2010
 *    1st week of 2017 starts on Sunday 1 January, 2017
 *
 * Calculations use UTC to avoid daylight saving issues.
 *
 * @param {Date} date - date to get week number of
 * @returns {number[]} year and week number
 */
function getWeekNumber(date) {
  // Copy date as UTC to avoid DST
  var d =  new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()));
  // Shift to the following Saturday to get the year
  d.setUTCDate(d.getUTCDate() + 6 - d.getUTCDay());
  // Get the first day of the year
  var yearStart = new Date(Date.UTC(d.getUTCFullYear(), 0, 1));
  yearStart.setUTCDate(yearStart.getUTCDate() - yearStart.getUTCDay());
  // Get difference between yearStart and d in milliseconds
  // Reduce to whole weeks
  return [d.getUTCFullYear(), (Math.ceil((d - yearStart) / 6.048e8))];
}

// Helper to format dates
function fDate(d) {
  var opts = {weekday:'short',month:'short',day:'numeric',year:'numeric'};
  return d.toLocaleString(undefined, opts);
}
// Parse yyyy-mm-dd as local
function pDate(s){
  var b = (s+'').split(/\D/);
  var d = new Date(b[0],b[1]-1,b[2]);
  return d.getMonth() == b[1]-1? d : new Date(NaN);
}
// Handle button click
function doButtonClick(){
  var d = pDate(document.getElementById('inp0').value);
  var span = document.getElementById('weekNumber');
  if (isNaN(d)) {
    span.textContent = 'Invalid date';
  } else {
    let [y,w] = getWeekNumber(d);
    span.textContent = `${fDate(d)} is in week ${w} of ${y}`;
  }
}

Date:<input id="inp0" placeholder="yyyy-mm-dd">
<button type="button" onclick="doButtonClick()">Get week number</button><br>
<span id="weekNumber"></span>