How to check if a key exists in AsyncStorage in React Native? getItem() always returns a promise object

Question

I'm trying to check whether a key is available in AsyncStorage with AsyncStorage.getItem('key_name'). If the key is not available it is not returning null, it still returns following promise object:

Promise
_45:0
_54:null
_65:null
_81:1

My function for getting data is as bellow:

checkItemExists(){
    let context = this;
    try {
        let value = AsyncStorage.getItem('item_key');
        if (value != null){
            // do something 
        }
        else {
            // do something else
        }
    } catch (error) {
    // Error retrieving data
    }
}

How can I check whether a key exists in AsyncStorage or not?

score 19 · Accepted Answer · edited Dec 23 '20 at 03:47

19

You need to add async await, or add .then to the result

async checkUserSignedIn(){
    let context = this;
    try {
       let value = await AsyncStorage.getItem('user');
       if (value != null){
          // do something 
       }
       else {
          // do something else
      }
    } catch (error) {
      // Error retrieving data
    }
}

edited Dec 23 '20 at 03:47

Community

1
1

answered May 22 '17 at 12:02

Sagar Khatri

1,004
8
23

Good answer, and this has nothing to do with the question, but you should use `const` instead of `let` when the value of the variable wont be reassigned. `let` is best used when the variable may be reassigned but not modified, `const` is used when it is neither reassigned nor modified. – ICW Sep 28 '19 at 22:19
@YungGun if it's for me my intention was only to show how to fetch value from asyncstorage and other stuff I just copied from OP's code. Nice point anyway. – Sagar Khatri Sep 30 '19 at 05:03
@SagarKhatri Am getting error like this when i use this code " await is a reserved word " > 61 | let value1 = await AsyncStorage.getItem('DriverId'); | ^ 62 | let value2 = await AsyncStorage.getItem('AccessToken'); 63 | console.log(value1 + " "+ value2) 64 | this.props.navigation.navigate('Login'); – Srinivasan Lakshmanan Oct 01 '19 at 07:47
@SrinivasanLakshmanan you need to use it with async before the function.. could you share you code please? – Sagar Khatri Oct 10 '19 at 12:58

score 8 · Answer 2 · answered May 22 '17 at 12:00

8

Like the name says, it's async. So you have to:

AsyncStorage.getItem('user')
.then((item) => {
     if (item) {
       // do the damage
     }
});

If needed, you can play either with local state or some application state management library.

answered May 22 '17 at 12:00

Samuli Hakoniemi

18,740
1
61
74

score 4 · Answer 3 · answered May 22 '17 at 12:00

AsyncStorage is async... so, you need to call it this way:

checkUserSignedIn(callback){
  AsyncStorage.getItem('user', (err, result) => {
    if (!err && result != null){
        // do something 
    }
    else {
        // do something else
    }
    callback(result);
  });
}

Jay Mayu · Answer 4 · 2020-08-23T05:06:18.903

You get a promise as error because you need to have await in your function call too. For example please find my general class and how I call it later in another call.

import AsyncStorage from "@react-native-community/async-storage";

const storageSet = async(key, value) => {
    try {
      await AsyncStorage.setItem(key, value);
    } catch(error) {
      console.log(error);
    }
}

const storageGet = async(key) => {
  try {
       const result = await AsyncStorage.getItem(key);
       console.log(result);
       return result;
    } catch(error) {
      console.log(error);
    }
}

export { storageSet, storageGet };

when I call them note the await keyword

 let value = await storageGet("somekey")
 if (value === null || value === undefined ) {
   //no value set in storage
 }

How to check if a key exists in AsyncStorage in React Native? getItem() always returns a promise object

4 Answers4