JavaScript sorting after concat of two arrays now working-CodePudding

I need some help. I've used a little function to concat two arrays and remove the duplicates:

let a = ['06.12.2021', '07.12.2021', '19.12.2021', '20.12.2021', '01.03.2022', '03.03.2022', '06.12.2021', '09.01.2022'];
let b = ['17.11.2021', '04.01.2022', '08.01.2022', '09.01.2022'];

let ab = [...new Set( a.concat( b ) )];

console.log(ab);

This works quite nice, but actually they are in a complete bad order. At least, they should start with the lowest date and ends with the highest. I've tried a sort function without any success:

let a = ['06.12.2021', '07.12.2021', '19.12.2021', '20.12.2021', '01.03.2022', '03.03.2022', '06.12.2021', '09.01.2022'];
let b = ['17.11.2021', '04.01.2022', '08.01.2022', '09.01.2022'];

let ab = [...new Set(a.concat(b))];

console.log(ab);

ab.sort((a, b) => Date.parse(b) - Date.parse(a));

console.log(ab);

Do you have any advice for me?

CodePudding user response：

I added a custom parse function that parses dates explicitly formatted as DD.MM.YYYY into Date objects. This fixes the date parse issue. I also changed b - a to a - b which sorts in increasing order.

let a = ['06.12.2021', '07.12.2021', '19.12.2021', '20.12.2021', '01.03.2022', '03.03.2022', '06.12.2021', '09.01.2022'];
let b = ['17.11.2021', '04.01.2022', '08.01.2022', '09.01.2022'];

let ab = [...new Set(a.concat(b))];

console.log(ab);

function parse(date) {
    const [d, m, y] = date.split('.');
    return new Date(y, m-1, d);
}

ab.sort((a, b) => parse(a) - parse(b));

console.log(ab);

CodePudding user response：

This is happening because some of the dates are not parseable in their current format and so can't be placed in the correct order. To test this yourself, try:

let a = ['06.12.2021', '07.12.2021', '19.12.2021', '20.12.2021', '01.03.2022', '03.03.2022', '06.12.2021', '09.01.2022'];
let b = ['17.11.2021', '04.01.2022', '08.01.2022', '09.01.2022'];

let ab = [...new Set(a.concat(b))];

let test = ab.map(m => new Date(m))

console.log(test);

This is because JavaScript dates are not equipped for handling DD.MM.YYYY formatted dates. If you don't mind using a library, something like DateJs may help

CodePudding user response：

With split() and sort() you can archive this:

const a = ['06.12.2021', '07.12.2021', '19.12.2021', '20.12.2021', '01.03.2022', '03.03.2022', '06.12.2021', '09.01.2022'];
const b = ['17.11.2021', '04.01.2022', '08.01.2022', '09.01.2022'];

const ab = [...new Set( a.concat( b ) )];

const newDates = ab.sort(function(a,b){
  return new Date(b.date) - new Date(a.date);
}).map(e => {
  const a = e.split(".");
  return a[2]   "."   a[1]   "."   a[0]
}).sort().map(e => {
  const a = e.split(".");
  return a[2]   "."   a[1]   "."   a[0]
})

console.log('newDates',newDates)