CODEWITHSUNDEEP
javascriptreact-nativeasynchronousasync-awaitasyncstorage
Vito Juliano
Vito Juliano

Reputation: 19

How can i do async/await in AsyncStorage react native?

So, this is my index.js in react native projects

import React, {useEffect} from 'react';
import {AppRegistry} from 'react-native';
import App from './App';
import {name as appName} from './app.json';

import {
  ApolloClient,
  HttpLink,
  ApolloLink,
  InMemoryCache,
  concat,
  ApolloProvider,
} from '@apollo/client';
import {setContext} from '@apollo/client/link/context';
import AsyncStorage from '@react-native-async-storage/async-storage';

const httpLink = new HttpLink({uri: 'https://dev.saba.id/graphql'});

const getToken = async () => {
  const token = await AsyncStorage.getItem('SESSION_TOKEN')
    .then(data => {
      if (data) {
        return data;
      } else {
        return;
      }
    })
    .catch(err => {
      console.log(err);
    });
  console.log('------------');
  console.log('console.log inside getToken function');
  console.log('Bearer ' + token);
  console.log('------------');
  return 'Bearer ' + token;
};

console.log('------------');
console.log('output of getToken function');
console.log(getToken());
console.log('------------');

const headerLink = setContext((request, previousContext) => ({
  headers: {
    // Make sure you include any existing headers!
    ...previousContext.headers,
    authorization: getToken(),
  },
}));

const client = new ApolloClient({
  link: headerLink.concat(httpLink),
  cache: new InMemoryCache(),
});

const Application = () => {
  return (
    <ApolloProvider client={client}>
      <App />
    </ApolloProvider>
  );
};

AppRegistry.registerComponent(appName, () => Application);

Okay, now just focus in getToken function and also a console.log beside that function.

In my mind, when we use async/await the function will return after token variables is done to solve their result, am i right?

But what i get for the output is really confusing for me.. getToken function returning more fast then await AsyncStore value.

This is the output of the code :

 BUNDLE  ./index.js 

 LOG  ------------
 LOG  output of getToken function
 LOG  {"_U": 0, "_V": 0, "_W": null, "_X": null}
 LOG  ------------
 LOG  Running "sabaCustomerApp" with {"rootTag":61,"initialProps":{}}
 LOG  ------------
 LOG  console.log inside getToken function
 LOG  Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJuYW1lIjoic2FiYSIsImVtYWlsIjoic2FiYUBnbWFpbC5jb20iLCJyb2xlIjoic3VwZXIgYWRtaW5pc3RyYXRvciIsImlhdCI6MTYyNzQ4ODY1MCwiZXhwIjoxNjMwMDgwNjUwfQ.W3vCNmIxsIyscJBk5aPMN3kqn7EVIEMLfZVgXqHB_UA
 LOG  ------------

Can you see? getToken() function retuning faster than console.log inside the function. How can it run like that?

What i want is, getToken() function returning a string such as "Bearer blablablabla"

Upvotes: 1

Views: 822

Answers (1)

Kelvin Schoofs
Kelvin Schoofs

Reputation: 8718

You're misunderstanding how async functions work.

When you call an async function, it actually wraps the function body in a Promise which gets returned:

async function test() {
    await ...;
    return 123;
}

const promise = test();
console.log(promise); // Promise
promise.then(result => console.log(result));
// ^ logs 123 at some point
console.log('continue'); // runs before .then(...)

If you want your function to wait for a Promise to resolve, it also has to be async and use the await keyword:

function waitSecond() {
    // This function isn't async, but still returns a Promise
    return new Promise(resolve => setTimeout(() => resolve(123), 1000));
}
async function otherFunction() {
    console.log(Date.now()); // x
    const result = await waitSecond();
    console.log(result); // 123
    console.log(Date.now()); // x+1000 (roughly)
}

I suggest reading this article and similar topics it mentions.

Upvotes: 2

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