JavaScript:每年几周

Question

在 javascript 中，我如何找出给定年份有多少周？从 year-dec-31 获取周数将失败，因为这可能导致第 1 周。

这个问题calculate number of weeks in a given year有点回答它，但是在 JS 中有什么巧妙的方法来计算它吗？

Answer 1

对于 ISO 8601 标准周

function getISOWeeks(y) {
  var d,
    isLeap;

  d = new Date(y, 0, 1);
  isLeap = new Date(y, 1, 29).getMonth() === 1;

  //check for a Jan 1 that's a Thursday or a leap year that has a 
  //Wednesday jan 1. Otherwise it's 52
  return d.getDay() === 4 || isLeap && d.getDay() === 3 ? 53 : 52
}
console.log(getISOWeeks(2019))
console.log(getISOWeeks(2020))
console.log(getISOWeeks(2021))

我从以下两篇文章中总结了这一点。

Calculating the number of weeks in a year with Ruby

javascript to find leap year