Iterating over nested JSON string in typescript

Question

I have a test nested JSON string.

const testString = `{
  "object1": {
    "5": [
      {
        "id": "A2OKPZ5S9F78PD",
        "rate": "2",
        "item": "item",
        "status": "status"
      }
    ]
  },
  "type": "LIVE_EVENT"
}`;

const model = JSON.parse(testString);
Object.values(model.object1).forEach((obj) =>
  obj.foreach((innerObj) => console.log(innerObj))
);

As you can see above I am trying to parse this as JSON and iterate over. The problem which I am facing during JSON.parse the inner object assumes the type undefined and foreach can not be applied on it. Can some one please help ?

Tried changing to this Object.values(model.object1).forEach(obj => (obj || []).foreach(innerObj => console.log(innerObj))); Still did not work — Dark Shadows, May 05 '20 at 04:58
Still does now work. Tried this. Object.values(model.object1).forEach(obj => (obj || []).forEach(innerObj => console.log(innerObj))); — Dark Shadows, May 05 '20 at 05:01
`model.object1` is indeed an object, so you need to iterate its properties https://stackoverflow.com/questions/684672/how-do-i-loop-through-or-enumerate-a-javascript-object — diedu, May 05 '20 at 05:01
I guess @diedu pointed out the problem. You need to use Object.values(obj) to get the array so you can use forEach on it. — vitkarpov, May 05 '20 at 05:04

Luís Ramalho · Accepted Answer · 2020-05-05T05:18:25.717

1

Your JSON is was invalid (before an edit) due to an extra comma after the status key/value pair and forEach() has an uppercase E. Also, as discussed in the comments below it seems you need to cast the inner obj to be of a type that understands forEach():

const testString = `{"object1":{"5":[{"id":"A2OKPZ5S9F78PD","rate":"2","item":"item","status":"status"}]},"type":"LIVE_EVENT"}`;
const model = JSON.parse(testString);
Object.values(model.object1).forEach((obj) =>
  (obj as any).forEach((innerObj) => console.log(innerObj))
);

edited May 05 '20 at 05:18

answered May 05 '20 at 05:04

Luís Ramalho

10,018
4
52
67

I am running the same code you pasted here on typescript. It says forEach can not be applied over undefined. – Dark Shadows May 05 '20 at 05:08
Check if your `JSON.parse(testString)` is actually parsing the json, i.e., log the `model` variable. – Luís Ramalho May 05 '20 at 05:10
@DarkShadows Can you share SS of that? – Chetan Kumar May 05 '20 at 05:11
Make sure that when you run the code above, you're actually having exactly the same `testString` as I do, because when I run locally it works. – Luís Ramalho May 05 '20 at 05:11
{ object1: { '5': [ [Object] ] }, type: 'LIVE_EVENT' } This is what i get after JSON.parse – Dark Shadows May 05 '20 at 05:11
error TS2339: Property 'forEach' does not exist on type 'unknown'. This is the exact error upon applying. – Dark Shadows May 05 '20 at 05:13
@DarkShadows if what you are getting is a typescript compile time error you could try casting the value so it doesn't complain `model.object1 as Array` – diedu May 05 '20 at 05:14
Try `(obj as any).forEach((innerObj) => console.log(innerObj))` – Luís Ramalho May 05 '20 at 05:15
1

@LuísRamalho Yes (obj as any) worked. Thank you very much. Can you update your answer so that I can mark as accepted. – Dark Shadows May 05 '20 at 05:16
Awesome, done. You should find the actual type of `obj` and not use `any`, maybe Array as @diedu pointed out. An array of the type of object that you have. – Luís Ramalho May 05 '20 at 05:19

Iterating over nested JSON string in typescript

1 Answers1