Formatting data with a foreach in Javascript

Question

I would like to make an API call with the data formatted like this.

[{"Id":10, “FolderID”:22},{"Id":12, “FolderID”:22}]

I have these different data sources below: (using redux)

const FolderId = indexes.currentFolder.id;

This is a constant value

const documentsId = indexes.copyDocuments;

this is the format of 8, 9 , 10

I tried to implement it by looping through the documents array with a foreach.

The only way i know how to attach the data is with an array but this creates a new array of each loop with is not what i want.

const data = [];

documentsId.forEach(function(doc){
  data.push(`"Id":${doc},"FolderID":${FolderId}`)
})

Does anyone know a way of doing this? Thanks.

maybe try something along the lines of: var tmp = {}; tmp.Id = doc.Id; tmp.FolderId = doc.FolderId; data.push(tmp); — Isaac Abramowitz
– Isaac Abramowitz, Commented Jul 16, 2018 at 16:54
what you want to do is quite simple. But can you provide more details on your arrays. Console what is documentsId . — Vikas
– Vikas, Commented Jul 16, 2018 at 16:56
I'm not sure how you're passing the FolderId in the following data.push("Id":${doc},"FolderID":${FolderId}) . If you're pushing an object to your array you can use data.push({"Id":`${doc}`,"FolderID":`${FolderId}`}. — Thomas
– Thomas, Commented Jul 16, 2018 at 17:01
when i try an use an object instead of an array it says its undefined — Great Khan 2016
– Great Khan 2016, Commented Jul 16, 2018 at 17:09

Jacob · Accepted Answer · 2018-07-16 17:16:34Z

2

The things you're passing into the data array are strings, when what you want is objects. Instead of:

data.push(`"Id":${doc},"FolderID":${FolderId}`)

....do:

data.push({ Id: doc, FolderID: FolderId })

...and data will be an array of objects instead of strings.

I'd also recommend using map like @JoeWarner suggested as a more succinct way to build the Array.

const data = documentsId.map(doc => ({ Id: doc, FolderID: FolderId }))

answered Jul 16, 2018 at 17:16

Jacob

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Comments

Joe Warner · Accepted Answer · 2018-07-16 17:21:49Z

What i believe you're looking for is the map prototype

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

what map does is return a new array from an orignal array so in your example we have an array of

[8, 9, 10]

we map over this the same way we'd use forEach it gets passed the item then the index

const newArray = [8, 9, 10].map(function (item, index) {
  return [item, index]
})
// [[8, 0], [9, 1], [10, 2]]

the map prototype returns a NEW array so no need to copy your array as to not mutate it this makes the map prototype immutable

const documentsId = [8, 9, 10]

/* however you get your folderId */
const folderId = 22;

const mappedToObjectArray = documentsId.map(id => ({id, folderId}))


/*
  If you're used to es5 this might look more familiar 

  function formatData() {
    return documentsId.map(function (doc) {
      return {
        id: doc,
        folderId: folderId
      }
    })
  }
*/

console.log(mappedToObjectArray)

Please let me know if i've misunderstood or you're confused about anything happy to help.

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