store.js

import React, { createContext, useContext, useState } from "react";
import { LogBox } from 'react-native';
import firebase from "./firebase.js";
const db = firebase.database();

export const StoreContext = createContext([]);

const StateProvider = ({ children }) => {
    const [isSignedIn,setIsSignedIn] = useState(false);
    const [username,setUsername] = useState('');
    const [score, setScore] = useState(0);

    const login = (username,password) =>{
        db.ref().child("users").child(username).once('value',
            function(snapshot) {
                if (snapshot.exists()) {
                    if(snapshot.val().password === password){
                        setUsername(username);
                        setScore(snapshot.val().score);
                        setIsSignedIn(true);
                    }
                    else {
                        alert("username and password do not match")
                    }
                }
                else {
                    let alertStr = "username: " + username + " does not exist";
                    alert(alertStr)
                }
            })
            .catch(function(error) {
                //console.error(error);
            });
    };

    const signUp =(username,password) => {
        db.ref().child("users").child(username).once('value',
            function(snapshot) {
                if (snapshot.exists()) {
                    alert("username already exists!")
                }
                else {
                    db.ref('users/' + username)
                        .set({
                            password: password,
                            score: 0,
                        });
                    setUsername(username);
                    setScore(0);
                    setIsSignedIn(true);
                }
            })
            .catch(function(error) {
                //console.error(error);
            });
    };

    return (
        <StoreContext.Provider
            value={{
                username,
                setUsername,
                score,
                setScore,
                isSignedIn,
                setIsSignedIn,
                login,
                signUp
            }}
        >
            {children}
        </StoreContext.Provider>
    );
};
export default StateProvider;
export const useStore = () => useContext(StoreContext);