javascript get key name from array of objects

Question

from

"data":[{"ja":"大阪市"},{"en":"Osaka"}]

I want to get "ja" and "en".

I tried several ways...

data.map(function(_, i) { return i; });

it returns array of numbers.

console.log(Object.keys(Object.values(data)));

all trials return

(2) [0, 1]
0: 0
1: 1

what can I do ?? please answer me. thank you.

data.map(x => Object.keys(x)[0]) Bad JSON design though. Would make far more sense if both keys and values just belonged to the same object. — Robby Cornelissen
– Robby Cornelissen, Commented Apr 9, 2019 at 1:28
The reason for the [0] is that, as I stated, your JSON is badly designed. — Robby Cornelissen
– Robby Cornelissen, Commented Apr 9, 2019 at 1:39

Maheer Ali · Accepted Answer · 2019-04-09 01:37:03Z

14

Use map() and return the first key the object. You can get keys using Object.keys()

let data = [{"ja":"大阪市"},{"en":"Osaka"}]
let res = data.map(x => Object.keys(x)[0]);
console.log(res)

If you don't want to use [0] use flatMap()

let data = [{"ja":"大阪市"},{"en":"Osaka"}]
let res = data.flatMap(x => Object.keys(x));
console.log(res)

Note: The second method will also get the other properties other than first. For example

[{"ja":"大阪市","other":"value"},{"en":"Osaka"}] //["ja","other","en"];

edited Apr 9, 2019 at 1:37

answered Apr 9, 2019 at 1:29

Maheer Ali

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Habeeb Okunade · Accepted Answer · 2021-01-09 22:38:26Z

4

let data = [{"ja":"大阪市"},{"en":"Osaka"}]
    
let res = data.reduce((arr, o) => {
  return Object.keys(o).reduce((a, k) => {
     if (a.indexOf(k) == -1) a.push(k);
        return a;
     }, arr)
  }, []);
    
console.log(res);

edited Jan 9, 2021 at 22:38

answered Jun 29, 2020 at 4:41

Habeeb Okunade

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