How to sort an array of objects by the date that are in string form?

Question

I am trying to sort a array of objects by their date.

Each object has a key time:

{
    accuracy: "15.455"
    eventId: "a7e81ca3-b840-4bb1-b41f-821722da4a5b"
    humidity: "50"
    latitude: "2.708813"
    location: {accuracy: {…}, latitude: {…}, longitude: {…}}
    longitude: "102.0083215"
    name: "Tag1"
    tags: {humidityOffset: {…}, rssi: {…}, dataFormat: {…}, 
           movementCounter: {…}, updateAt: {…}, …}
    temperature: "28.26"
    time: "2020-10-18T01:46:00+0800"
}

I have tried using the following function which I made based on this question but the dates do not get sorted.

 const sortTagsByDate = (array) => {
    const stringToDate = array.map(data => new Date(data.time));
    const sortData = stringToDate.sort((a,b)=> b.time - a.time);
    return sortData;
}

When I console log the output of the function above the dates are converted to a DateTime but not sorted and only the time gets returned.

Sun Oct 18 2020 01:42:17 GMT+0800 (Malaysia Time)
Tue Oct 20 2020 23:04:51 GMT+0800 (Malaysia Time)
Sun Oct 18 2020 01:42:35 GMT+0800 (Malaysia Time)

you are returning a sorted array of dates. not a sorted array of objects. — GottZ
– GottZ, Commented Oct 21, 2020 at 15:39
When the dates are subtracted, each date is converted to its valueOf(). No need to do it explicitly. — AlexH
– AlexH, Commented Oct 21, 2020 at 15:41
Also, I believe new Date.valueOf will return the current timestamp if you don't initialize it with the string. — AlexH
– AlexH, Commented Oct 21, 2020 at 15:42
By the way, you don't need to convert ISO 8601 formatted dates into a Date to compare them. Lexicographical sorting acts as chronological sorting for them. EDIT: assuming they are in the same timezone, that is. — VLAZ
– VLAZ, Commented Oct 21, 2020 at 15:42

AlexH · Accepted Answer · 2020-10-21 15:48:36Z

1

Instead of b.time - a.time, try b.getTime() - a.getTime(). Here's an example:

const sortTagsByDate = (array) => {
    return array.sort((a,b)=> a.time.localeCompare(b.time));
}

let example1 = { time: "2020-10-18T01:46:00+0800" };
let example2 = { time: "2020-10-18T01:47:00+0800" };
let example3 = { time: "2020-10-18T01:48:00+0800" };
let exampleArray = [example1, example2, example3];

console.log(sortTagsByDate(exampleArray));

edited Oct 21, 2020 at 15:48

answered Oct 21, 2020 at 15:39

AlexH

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4 Comments

yudhiesh Over a year ago

Hi this works but as I mentioned I want the objects to be sorted based on the date.

AlexH Over a year ago

Should work now. Used @VLAZ's suggestion of lexicographical sorting.

yudhiesh Over a year ago

Yes it does I wanted it sorted from oldest to newest so i just changed it a bit return array.sort((a,b)=> a.time.localeCompare(b.time));

AlexH Over a year ago

I've updated my answer. If it works, would you mind accepting the answer?

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