Unable to handle case of null variable retrieved from AsyncStorage

I am trying to do something very simple in my react native log in screen. I first try and get the userId of a user, and if it's not set, I want to redirect to the user's login page. When the userId is not set, I console out and get a null value for it. But when I check if userId === null, it doesn't work. Any ideas on what I am doing wrong?

const userId = await AsyncStorage.getItem('userId');
console.warn(userId);
console.warn("When userId is not set I get a value of null");
if (userId === null) {
    console.warn("However this check for null is not working");
    navigation.navigate("UserLoginWeb");
}

This is a common issue with AsyncStorage in React Native. The potential issues here could be:

• AsyncStorage always returns strings or null. Sometimes it might return the string "null" instead of actual null, which would make === null fail.

  • The check should handle both cases:

    if (userId == null || userId === 'null')
    

• It's important to wrap AsyncStorage operations in try-catch blocks since they can fail.

The code below is a proper way to handle this:

import React, { useEffect } from 'react';
import AsyncStorage from '@react-native-async-storage/async-storage';

const CheckUserAuth = ({ navigation }) => {
  useEffect(() => {
    const checkUserId = async () => {
      try {
        const userId = await AsyncStorage.getItem('userId');
        console.warn('userId value:', userId);
        
        // Correct way to check for null/undefined
        if (userId == null || userId === 'null') {
          console.warn('User is not logged in');
          navigation.navigate('UserLoginWeb');
        } else {
          console.warn('User is logged in with ID:', userId);
        }
      } catch (error) {
        console.error('Error reading userId from AsyncStorage:', error);
        navigation.navigate('UserLoginWeb');
      }
    };

    checkUserId();
  }, [navigation]);

  return null; // Or your loading component
};

export default CheckUserAuth;

The above code uses proper error handling, handles both null and "null" cases, and is wrapped in useEffect to properly handle the async operation. It also includes proper TypeScript/Flow-friendly type checking.

Make sure you're awaiting the check in a proper async context. If the code is directly in your component body rather than in a useEffect or async function, it won't work correctly. I hope this helps.