Extracting one value from array into a variable - ReactJS

Question

I know that maybe i will sound stupid for some people , but i am trying to extract single value from my array and insert it into a variable . How was possible to do it . In my case i want to have a new variable with the value only of the fileId

const arrayOfFiles = rowData.files;

Output :

[{…}, {…}]
0: {fileId: 166, fileExtension: "CSV"}
1: {fileId: 167, fileExtension: "XLSX"}
lastIndex: (...)
lastItem: (...)
length: 2
__proto__: Array(0)

Tryout

 arrayOfFiles.forEach(file=> console.log(file.fileId));

Output

166
167

But how can i insert this value into a single variable ? I gave a try something like this :

const fileId = arrayOfFiles.forEach((file) => file.fileId);

But it returns me undefined . Any suggestions what am i doing wrong ?

What value do you expect fileId to have? 166 or 167? Or maybe an array with both? Or is that not what you're asking? — rid
– rid, Commented May 20, 2020 at 10:14
Basically const fileId should be equal to file.fileId , because on click i can detect which id is requested — PandaMastr
– PandaMastr, Commented May 20, 2020 at 10:17

Viral Rathod · Accepted Answer · 2020-05-20 10:22:47Z

1

const arrayOfFiles = [{fileId: 166, fileExtension: "CSV"}, {fileId: 167, fileExtension: "XLSX"}];
var ids = arrayOfFiles.map((file) => file.fileId);
console.log(ids)

answered May 20, 2020 at 10:22

Viral Rathod

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2 Comments

PandaMastr Over a year ago

Not exactly . I am not expecting new arrays of files.fileId

Viral Rathod Over a year ago

What you are expecting? I thought you want - how can i insert this value into a single variable ?

pope_maverick · Accepted Answer · 2020-05-20 10:36:27Z

0

the problem is with the forEach, unlike map, filter, reduce, find, etc.. it doesn't return any value, hence you're getting undefined.

const res = arrayOfFiles.forEach(file => file.fileId); // undefined

const res = arrayOfFiles.map(file => file.fileId); // [166, 167]

const res = arrayOfFiles.filter(file => file.fileId === 166); // [166]

const res = arrayOfFiles.find(file => file.fileId === 166); // 166

answered May 20, 2020 at 10:36

pope_maverick

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