Firebase returning "undefined" value in React Native data fetch

Question

I am trying to fetch a list of Restaurants from the firebase realtime database,
my code snipped for that fetching the data -

_isMounted = false;

state :{
  data: [],
}

constructor(props){
  super(props)

  this.state = {
    data:[],
  }
}

componentDidMount(){
  this._isMounted = true
  this.getData()
}

componentWillUnmount(){
  this._isMounted = false
}

getData(){
  firebase.database().ref('Restaurants/').on("value", snapshot =>{
    let restaurantList = snapshot.val();
    console.log(restaurantList)
    this.setState({data: restaurantList})
  });
}

The data structure on Firebase is as follows -

The console output for the array restaurantList is -

Array [
  undefined,
  Object {
    "location": "Testing data",
    "name": "Time Traveller",
    "rating": 4.5,
    "tags": "Indian, Asian",
  },
  Object {
    "locations": "Testing data",
    "name": "Novelty",
    "rating": 4.5,
    "tags": "Indian",
  },
]

I am not sure from where I am getting the undefined item in the array.

Peter Haddad · Accepted Answer · 2019-12-13 05:20:38Z

3

Try the following:

getData(){
  firebase.database().ref('Restaurants/').on("value", snapshot =>{
  snapshot.forEach((childSub) => {
    let key = childSub.key;
    let restaurantList = childSub.val();
    console.log(restaurantList);
   });
  });
}

The undefined is the key, try iterating inside the keys and retrieving the data

answered Dec 13, 2019 at 5:20

Peter Haddad

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