JavaScript: sort an array of timestamps with day–month

I have an array of timestamps or strings that are of this format - day–month–year. e.g ['03-11-2018', '04-12-2018', '10-01-2017', '10-12-2017']

And I want to sort them chronologically so the above array would become [ '10-01-2017', '10-12-2017', '03-11-2018', '04-12-2018' ]

I am aware that you can use moment.js to do this but I want to write this by hand without using any 3rd lib.

Here is my attempt:

function sortTimestamp(array) {
  array.sort((time1, time2) => {
    const [day1, month1, year1] = time1.split('-')
    const [day2, month2, year2] = time2.split('-')
    return year2 > year1
      ? -1
      : year2 < year1
      ? 1
      : month2 > month1
      ? -1
      : month2 > month1
      ? 1
      : day2 > day1
      ? -1
      : 1
  })
}

It works ok but it is not really readable and it is a very imperative approach. I wonder if there is a better way to do it and also ideally it can be extended to support that other date formats e.g. month–day–year.

CodePudding user response：

An alternative is to specify with extra arguments what the format is (regex) and how it should be reordered to ISO-style YYYYMMDD format. Then the function can perform that replacement and do a lexical sort:

function sortTime(array, regex, iso) {
    let fmt = time => time.replace(regex, iso);
    return array.sort((time1, time2) => 
        fmt(time1).localeCompare(fmt(time2)));
}

// demo
let dates = ['03-11-2018', '04-12-2018', '10-01-2017', '10-12-2017'];
let result = sortTime(dates, /(..)-(..)-(....)/, "$3$2$1");
console.log(result);

So if the input should be interpreted as mm-dd-yyyy instead of dd-mm-yyyy, then make the third argument "$3$1$2" instead of "$3$2$1".

CodePudding user response：

It's a little simpler using subtraction rather than nested ternaries.

function sortTimestamp(array) {
  array.sort((time1, time2) => {
    const [day1, month1, year1] = time1.split('-')
    const [day2, month2, year2] = time2.split('-')
    return year1 - year2 || month1 - month2 || day1 - day2;
  })
}

CodePudding user response：

You can first convert them to Date objects then use the getTime functionality to compare for sorting. A similar question was answered here

const dates = ['03-11-2018', '04-12-2018', '10-01-2017', '10-21-2017']

sortedDates = dates.sort((a,b)=>{
  const dateA = new Date(a)
  const dateB = new Date(b)
  //change the comparison sign for required orde
  return dateA.getTime() < dateB.getTime() 
  ? 1 
  : -1
 
})
console.log(sortedDates)

CodePudding user response：

Similar to Craques answer, but added both ASC, DESC sorting using the getTime method

ASC:

dates.sort((a,b) => new Date(a).getTime() - new Date(b).getTime())

DESC:

dates.sort((a,b) => new Date(b).getTime() - new Date(a).getTime())