How to sort an array of objects by multiple date fields?-CodePudding

I have the following data structure:

var dates = [
  {
    id: '1',
    date1: '2022-03-21T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '2',
    date1: '2022-03-20T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '3',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '4',
    date2: '2022-03-15T18:59:36.641Z',
  }
];

var sorted = dates.sort(function(a,b) {
      return (a.date1 > b.date1) ? 1 : -1
   });

console.log({sorted});

Notice that date1 is not always available, but date2 is required. I'd like to sort by date1 first, then date2. I've created this fiddle to test, but still haven't figured it out: https://jsfiddle.net/y9sgpob8/4/

Please help me figure out how to get the results in the following order:

[{
  date1: "2022-03-20T18:59:36.641Z",
  date2: "2022-03-17T18:59:36.641Z",
  id: "2"
}, {
  date1: "2022-03-21T18:59:36.641Z",
  date2: "2022-03-17T18:59:36.641Z",
  id: "1"
}, {
  date2: "2022-03-15T18:59:36.641Z",
  id: "4"
}, {
  date2: "2022-03-17T18:59:36.641Z",
  id: "3"
}]

CodePudding user response：

You could also separate the objects that only have date2 then sort and lastly merge it. See snippet below:

const dates = [
  {
    id: '1',
    date1: '2022-03-21T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '2',
    date1: '2022-03-20T18:59:36.641Z',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '3',
    date2: '2022-03-17T18:59:36.641Z',
  },
  {
    id: '4',
    date2: '2022-03-15T18:59:36.641Z',
  }
];

var array1 = [];
var array2 = [];

for (const date in dates) {
  if (dates[date].date1) {
    array1.push(dates[date]);
  } else {
   array2.push(dates[date]);
  }
}

var sorted1 = array1.sort(function(a,b) {
      return (a.date1 > b.date1) ? 1 : -1
   }); 
   
var sorted2 = array2.sort(function(a,b) {
      return (a.date2 > b.date2) ? 1 : -1
   }); 
   
const merge = sorted1.concat(sorted2);  
console.log(merge);

CodePudding user response：

You need to sort based on

whether date1 exists
then based on date1 value
then based on date2 value

Since the dates are in ISO format, you can do string comparison to sort

const input=[{id:"1",date1:"2022-03-21T18:59:36.641Z",date2:"2022-03-17T18:59:36.641Z",},{id:"2",date1:"2022-03-20T18:59:36.641Z",date2:"2022-03-17T18:59:36.641Z",},{id:"3",date2:"2022-03-17T18:59:36.641Z",},{id:"4",date2:"2022-03-15T18:59:36.641Z",}];

input.sort((a,b) => 
  ( ('date1' in b) - ('date1' in a) )
  || (a.date1 ?? '').localeCompare(b.date1 ?? '')
  || a.date2.localeCompare(b.date2)
)

console.log(input)