Can't get the data from array react and Firestore - reactjs

Question

How can I access the value exist from an array? I think I didn't pass the array inside? Any help or advice
var isExist = this.props.isFavorite(this.props.code);
console.log(isExist)
I have this variable isExist containing the response from console below.
[]
client: [id: "LvR05w9v9xrC3r4V1W8g", exist: true]
length: 1
_proto_:Array(0)
How can I access the exist in my array? When I tried isExist[0].exist I'm getting an error. Any help?
isExist.exist = Undefined
isExist[0].exist = TypeError: Cannot read property 'exist' of undefined
favorite method where I am accessing and pushing data to the array
export const isFavorite = (data) => dispatch => {
let exist = [];
var clientQuery = firebase.firestore().collection(path).where('client_id', '==', data);
clientQuery.get().then((querySnapshot) => {
querySnapshot.forEach((doc) => {
var data = [];
data.id = doc.id;
data.exist = doc.exists;
exist.push(data)
});
});
return exist;
}

Answer 1

isFavorite returns a function which takes one argument dispatch and returns exist array. You seem to use async code to populate exist array. So when that function returns exist is an empty array []. You either need to continue using promises or use await. And you need to call the function returned by isFavorite.
If this.props.isFavorite and const isFavorite are not the same then add the code for this.props.isFavorite please.

Answer 2

You're creating an array Object. Then the array object {data}[]. So the problem is, the data is actually not only an array but also an object.
Try doing this.
var data;
data.id = doc.id;
data.exist = doc.exist;
exist.push(data);
Now you will have exist data that would be an array of Object.
Then iterate from it.
exist[0].id;
//or try
exist[0].data.id;
//Depends on how you implement your data.

Answer 3

Since client array doesn’t contain object with keys and values I would recommend you to try with array of index with split() to get id value and exist value from array like
Like
var isExist = this.props.isFavorite(this.props.code);
var id = isExist.client[0];
var exist = isExist.client[1];
var idValue = id ? id.split(': '): '';
console.log(idValue);
const existValue = exist ? exist.split(': '): false;
console.log(existValue);
And here change data = []; array to data ={}; object
querySnapshot.forEach((doc) => {
var data = {};
data.id = doc.id;
data.exist = doc.exists;
exist.push(data)
});