CODEWITHSUNDEEP
javascriptarraysdatedatetime
Erandall
Erandall

Reputation: 55

Javascript: Array of milliseconds to array of dates

I've got some behavior I don't understand when I'm trying to take my input array of milliseconds and change them to dates with Date(). For example:

0: 1582641000
1: 1582727400
2: 1582813800
3: 1582900200
4: 1583159400
5: 1583245800
6: 1583332200
7: 1583418600
8: 1583505000
9: 1583760600
10: 1583847000

So far I've used pretty simple functions to do this, like:

for (i = 0; i < timestamp.length; i++) {
    timestamp[i] = Date(timestamp[i]);
}

Strangely, to me at least, this makes every element of "timestamp" the same date value. Similarly, if I do:

for (i = 0; i < timestamp.length; i++) {
    timestamp[i] = new Date(timestamp[i]);
}

Now every date in the "timestamp" array is in Jan 19 1970. What's going on here? How can I get the correct human readable string array from this? I.E.: Mar 25 2020 20:50:00 GMT-0700 (PDT)?

Upvotes: 1

Views: 464

Answers (1)

CertainPerformance
CertainPerformance

Reputation: 370619

The Date constructor accepts milliseconds as a single parameter, not seconds. Multiply the number by 1000 first.

You also must use new, otherwise the resulting date string will be at the current time, not the timestamp of the parameter. (All arguments are ignored without new)

Use .map instead of a for loop, and call toUTCString:

const arr = [
  1582641000,
  1582727400,
  1582813800,
  1582900200,
  1583159400,
  1583245800,
  1583332200,
  1583418600,
  1583505000,
  1583760600,
  1583847000,
];
const arrOfDates = arr.map(secs => new Date(secs * 1000).toUTCString());
console.log(arrOfDates);

Upvotes: 2

Related Questions