Javascript - 按当前月份的时间顺序对月份数组进行排序

Question

I have a list of months in javascript. I want to sort it in chronological order based on the current date.

Example monthsArr = ["March", "February", "November", "December", "January"]

if current month is November, sorted array should be ["Nov", "Dec", "Jan", "Feb", "Mar"]

if current month is Jan, sorted array should be ["Jan", "Feb", "Mar", "Nov", "Dec"]

Don't worry about conversions to enums or key value pairs. It can be handled. What I am looking for is the logic on how to implement this sort function.

Answer 1

like this:

 var months = { January: 0, February: 1, March: 2, April: 3, May: 4, // et&c November: 10, December: 11 }; var monthsArr = ["March", "February", "November", "December", "January"]; var month = new Date().getMonth(); monthsArr.sort(function(m1, m2) { var n1 = months[m1], n2 = months[m2]; if (n1 < month) { n1 = n1 + 12; } if (n2 < month) { n2 = n2 + 12; } return n1 - n2; }); console.log(monthsArr);

have a mapping from name and month number like

var months =
{
  January: 0,
  February: 1,
  March: 2,
  April: 3,
  May: 4,
  // et&c
  November: 10,
  December: 11
};

get the current month

var month = new Date().getMonth();

sort the array adding 12 to months that are earlier than month . that puts them after months that are the same as this month or later.

monthsArr.sort(function(m1, m2)
{
  var n1 = months[m1], n2 = months[m2];
  if (n1 < month)
  {
    n1 = n1 + 12;
  }
  if (n2 < month)
  {
    n2 = n2 + 12;
  }
  return n1 - n2;
});

Answer 2

I would suggest you to get the index of current month,
and then use array slice to recompose the array starting from that index:

 var m = [ "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"] var cur = new Date().getMonth() var sorted = [...m.slice(cur), ...m.slice(0,cur)] console.log(sorted)

Answer 3

You could take an object for the month values and take a wanted month to be the first and sort by a check if the actual month is smaller than the first month or by the month value.

 function sort(array, first) { var months = { January: 1, February: 2, March: 3, April: 4, May: 5, June: 6, July: 7, August: 8, September: 9, October: 10, November: 11, December: 12 }; return array.sort((a, b) => (months[a] < months[first]) - (months[b] < months[first]) || months[a] - months[b] ); } console.log(...sort( ["March", "February", "November", "December", "January"], "November")); console.log(...sort( ["March", "February", "November", "December", "January"], "January"));