How to check number exists in Firebase Database? - react-native-firebase - react-native

Question

I use react native through firebase database
I have a database creating products each product has a number
I want to take a number and compare it with the product number
And if there is then I want to get a product
the function its give me my correct name but where i use it on render its not found the variable (name)
getAllContact = async key => {
let barCodeData2 = this.props.navigation.state.params.barcodeData
let self = this;
let contactRef = firebase.database().ref()
contactRef.on("value", dataSnapsot => {
if (dataSnapsot.val()) {
let contactResult = Object.values(dataSnapsot.val())
let contactKey = Object.keys(dataSnapsot.val())
contactKey.forEach((value, key) => {
contactResult[key]["key"] = value
})
self.setState({
fname: contactResult.fname,
data: contactResult.sort((a, b) => {
var nameA = a.barcode
var nameB = barCodeData2
const name = a.fname
console.log(`${nameA} What numers issssssss`);
if (nameA == nameB) {
alert(`${name} ........`)
console.log(`${nameA == nameB}is Equqlqlqlql`);
return name
}
}),
})
}
})
}
render() {
let t=this.state.name
alert(`${t} how?`)// is give Not found
// let d = this.props.navigation.state.params.barcodeData
return (
)
}

Answer 1

When you try such a comparison query i.e.
let ref = firebase.firestore();
ref.collection('zoo')
.where("id", "==", myID)
.get()
.then((snapshot) => {
console.log(snap.empty); //this will denote if results are empty
snapshot.forEach(snap => {
console.log(snap.exists); //alternatively this will also tell you if it is empty
})
})

Answer 2

well what you can do is run query based on you product no and if there's a product you will a product if there's none you will get an empty array.
read firebase documentation on queries
https://firebase.google.com/docs/reference/js/firebase.database.Query