React Native - Promise 返回未定义

Question

I have a js file that returns whether I have internet connection or not, and then in another js I have an if else statement that gets that value. The thing is im getting connection = undefined.

import React from 'react';
import NetInfo from "@react-native-community/netinfo";

const isConnected = function() {
  NetInfo.fetch().then(state => {
    console.log("state.isConnected: ", state.isConnected)
    return state.isConnected
  });
}

export default isConnected;

import isConnected from '../../src/utils/internetConnection';

async checking(){
   var connection = await isConnected()
   console.log("connection : ", connection)
   if (connection){
      return true
   }

   Alert.alert("There is no Internet connection")
   return 
} 

Answer 1

Your isConnected function is not a promise. If you wish to use async/await, isConnected must be a promise.

Try this:

const isConnected = function() {
  return new Promise((resolve, reject) => {
    NetInfo.fetch().then(state => {
      console.log("state.isConnected: ", state.isConnected)
      resolve(state.isConnected);
    })
    .catch(err => {
      reject(err)
    })
  })
}

Answer 2

try this instead

export const isConnected = async function () {
    var networkState = await NetInfo.fetch()
    return networkState.isConnected
}

Answer 3

I am not 100% sure on this, but it could be as simple as

 const isConnected = function() { return NetInfo.fetch().then(state => { console.log("state.isConnected: ", state.isConnected) return state.isConnected }); }

Answer 4

Because you didn't return anything in isConnected function. let's try this code:

const isConnected = async function() {
  const { isConnected } = await NetInfo.fetch()

  return isConnected;
}

async checking(){
  var connection = await isConnected()

  return Boolean(connection)
}