Modify an array of objects with for in

Question

I'm trying to format a date inside an object.

I'm currently have the next array of objects:

    [
      { date: 2022-01-03T05:00:41.560Z },
      { date: 2022-01-03T22:54:33.980Z },
      { date: 2022-01-03T22:50:26.920Z },
      { date: 2022-01-03T22:32:29.660Z },
      { date: 2022-01-03T22:22:58.480Z }
    ]

And I'm trying to do the next:

    for (const prop in obj) {
        obj[prop].date = moment(obj[prop].date).tz("America/Vancouver").format("YYYY-MM-DD");
    }

Expecting:

    [
      { date: 2022-01-02 },
      { date: 2022-01-03 },
      { date: 2022-01-03 },
      { date: 2022-01-03 },
      { date: 2022-01-03 }
    ]

But I can't

let obj = [
{ date: "2022-01-03T05:00:41.560Z" },
{ date: "2022-01-03T22:54:33.980Z" },
{ date: "2022-01-03T22:50:26.920Z" },
{ date: "2022-01-03T22:32:29.660Z" },
{ date: "2022-01-03T22:22:58.480Z" }
];
for (const prop in obj) {
  obj[prop].date = moment(obj[prop].date).tz("America/Vancouver").format("YYYY-MM-DD");
}
console.log(obj)

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.4/moment-with-locales.min.js" integrity="sha512-42PE0rd+wZ2hNXftlM78BSehIGzezNeQuzihiBCvUEB3CVxHvsShF86wBWwQORNxNINlBPuq7rG4WWhNiTVHFg==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

modify it, I keep getting the original array

Your data is an array of objects so you probably want for...of instead: for (const obj of data) {...}. — Andy
– Andy, Commented Jul 7, 2022 at 14:13
The code,as is in your example, seems to work fine (*see jsfiddle.net/cdysmvf3). Perhaps your data is coming from an immutable source and so you cannot modify them. Where do you get the obj from ? — Gabriele Petrioli
– Gabriele Petrioli, Commented Jul 7, 2022 at 14:26
Please update the snippet to a minimal reproducible example - I could not find the correct moment from cdn to help you — mplungjan
– mplungjan, Commented Jul 7, 2022 at 14:33
@Gabriele Petrioli I'm getting it from a db.collection.find().then(()=>{}) — Legion
– Legion, Commented Jul 7, 2022 at 14:47
I wonder if the problem is due to moment-timezone installation not having the Vancouver data. With plain old moment, and .utcOffset('-7:00'), (and a little syntax cleanup) I see your code working just fine. — danh
– danh, Commented Jul 7, 2022 at 15:01

Xavier B. · Accepted Answer · 2022-07-07 14:15:19Z

3

I recommend to use Array.map for this transformation:

const data = [
  { date: '2022-01-03T05:00:41.560Z' },
  { date: '2022-01-03T22:54:33.980Z' },
  { date: '2022-01-03T22:50:26.920Z' },
  { date: '2022-01-03T22:32:29.660Z' },
  { date: '2022-01-03T22:22:58.480Z' }
];

const res = data.map(
  ({ date }) => ({
    date: moment(date).tz("America/Vancouver").format("YYYY-MM-DD")
  })
);

console.log(res);

in this example we are deconstructing each object and only extracting date, and return a new object that's only got date in it

Taking below comments into account, try Array.forEach:

data.forEach(
  ({ date }, index) => {
    data[index].date = moment(date).tz("America/Vancouver").format("YYYY-MM-DD");
  }
);

edited Jul 7, 2022 at 14:15

answered Jul 7, 2022 at 14:14

Xavier B.

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1 Comment

evolutionxbox Over a year ago

This doesn't modify data which the OP seems to want

danh · Accepted Answer · 2022-07-07 15:04:18Z

1

For what it's worth, here's the OP snippet running, improved slightly by using for-of, and (not sure if this is an improvement or a work-around) by using the native timezone offset.

let data = [
  { date: "2022-01-03T05:00:41.560Z" },
  { date: "2022-01-03T22:54:33.980Z" },
  { date: "2022-01-03T22:50:26.920Z" },
  { date: "2022-01-03T22:32:29.660Z" },
  { date: "2022-01-03T22:22:58.480Z" }
];

for (const obj of data) {
  obj.date = moment(obj.date).utcOffset('-7:00').format("YYYY-MM-DD");
}
console.log(data);

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.29.4/moment.min.js"></script>

answered Jul 7, 2022 at 15:04

danh

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