How to loop on a JSON data and put part of it in another array?

Question

I want to loop on a JSON data and put a part of it in a sperate array.

I have this JSON data:

{"msg":"[{"parent":"0","child":"1"},{"parent":"0","child":"2"}]","sig":"3045022100b3f03c83ed1f3d0bc72475550f23c0dd38277b0e2230e1fe76611577b2ca4b7e022037c77d37cc08ed897d0d1a11d09342e6abb73e641d20d5d55f367044d5489ddf"}

I want to make an array of msg only like this:

[ '0', '1', '0', '2 ]

My code:

var message = '[{"msg":[{"parent":"0","child":"1"},{"parent":"0","child":"2"}],"sig":"3045022100b3f03c83ed1f3d0bc72475550f23c0dd38277b0e2230e1fe76611577b2ca4b7e022037c77d37cc08ed897d0d1a11d09342e6abb73e641d20d5d55f367044d5489ddf"}]'
var g = [];
const jsArray = JSON.parse(message);
Array.from(jsArray.msg).forEach(jsdata => {
  console.log(jsdata)
  g.push(jsdata.parent, jsdata.child)
})
console.log(g);

I could not meet what I really want it says:

[
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined, undefined, undefined,
  undefined, undefined, undefined, undefined,
  ... 10 more items
]

How could I solve this, please? Thanks in advance

Does msg contain String value? If so, you need to JSON.parse that as well: Array.from(JSON.parse(jsArray.msg)) — Diyorbek Sadullaev
– Diyorbek Sadullaev, Commented Mar 6, 2021 at 17:10
The JSON string is not valid JSON. The array contained in msg cannot be quoted to be legit. — Randy Casburn
– Randy Casburn, Commented Mar 6, 2021 at 17:17
As you can see, your code produces a syntax error because the JSON is malformed. Please edit your question to provide the actual JSON string. — Randy Casburn
– Randy Casburn, Commented Mar 6, 2021 at 17:24

Randy Casburn · Accepted Answer · 2021-03-06 17:26:33Z

2

It is as simple as using the .map method to gather the data and then flatting the final array to get you output.

var message ='[{"msg":[{"parent":"0","child":"1"},{"parent":"0","child":"2"}],"sig":"3045022100b3f03c83ed1f3d0bc72475550f23c0dd38277b0e2230e1fe76611577b2ca4b7e022037c77d37cc08ed897d0d1a11d09342e6abb73e641d20d5d55f367044d5489ddf"}]';

let data = JSON.parse(message);
let output = data[0].msg.map(d=>[d.parent,d.child]).flat();
console.log(output);

answered Mar 6, 2021 at 17:26

Randy Casburn

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Beshambher Chaukhwan · Accepted Answer · 2021-03-06 17:59:31Z

1

Try the code below to loop the inner array:

    var message ='[{"msg":[{"parent":"0","child":"1"},{"parent":"0","child":"2"}],"sig":"3045022100b3f03c83ed1f3d0bc72475550f23c0dd38277b0e2230e1fe76611577b2ca4b7e022037c77d37cc08ed897d0d1a11d09342e6abb73e641d20d5d55f367044d5489ddf"}]';
    let g=[];
    const jsArray = JSON.parse(message);
    jsArray.forEach(jsMsgData => {
         // console.log(jsMsgData.msg);
         jsMsgData.msg.forEach(jsdata => {
            g.push(jsdata.parent, jsdata.child);
         })
    });
    console.log(g);

check full code here: https://ideone.com/QywYfb

edited Mar 6, 2021 at 17:59

answered Mar 6, 2021 at 17:16

Beshambher Chaukhwan

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4 Comments

Beshambher Chaukhwan Over a year ago

I assume he is getting data from an api call so json format should be correct or else he won't get lots of undefined values pushed in g right

ismsm Over a year ago

Thanks for answering! The link of full code is not working. Could you please check the link?

Beshambher Chaukhwan Over a year ago

Its working for me I checked in incognito mode so no access issues. Maybe your firewall is blocking it.

Beshambher Chaukhwan Over a year ago

I converted it into code snippet now try it @ismsm

Omle · Accepted Answer · 2021-03-06 18:00:16Z

0

For working with JSON as a JS you will have to use JSON.parse(). This will spread your JSON object to an Array instance with its attribute . Then you can loop over the array and do whatever you like. When you are done with the instance and you want to pass it to a function , use JSON.stringify() to convert the Object to a string (which you can write or pass)

answered Mar 6, 2021 at 18:00

Omle

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