Function inside a Function not calling in React Native - function

Question

I am new to react-native and calling a function inside a fucntion.
I have done as below so far :
Step 1 : Created a function _snapshotToArray to convert the firebase snapshot to Arrray.
_snapshotToArray(snapshot) {
var returnArr = [];
snapshot.forEach(function(childSnapshot) {
var item = childSnapshot.val();
item.key = childSnapshot.key;
returnArr.push(item);
});
return returnArr;
}
Step 2 : Created another function as below and calling _snapshotToArray inside it.
_readUserDataFromFirebaseConsole() {//once and on
firebase.database().ref('Users/').on('value', function (snapshot) {
console.log(this._snapshotToArray(snapshot));
Toast.show(this._snapshotToArray(snapshot),Toast.LONG);
});
}
Talking about this call :
console.log(this._snapshotToArray(snapshot));
When I press CTRL+CLick, it not letting me to navigate to body of the fuction _snapshotToArray.
In Device am getting below error :
_snapshotToArray is not defined
What might be the issue ?

Answer 1

I'm not at my PC right now, so I cannot test it, but from looking at your code, you need to use a different function notation to allow the varibale access of/from parent methods and parent class.
_snapshotToArray = snapshot => {
var returnArr = [];
snapshot.forEach(function(childSnapshot) {
var item = childSnapshot.val();
item.key = childSnapshot.key;
returnArr.push(item);
});
return returnArr;
}
and
_readUserDataFromFirebaseConsole = () => {
firebase.database().ref('Users/').on('value', snapshot => {
console.log(this._snapshotToArray(snapshot));
Toast.show(this._snapshotToArray(snapshot),Toast.LONG);
});
}