无法使用 nodejs 导出访问变量值？

Question

Hey i have fallen into a situation where i cannot access a variable which i have set within a nodejs module which i have exposed with module exports to access from the main file, i will show you below:

Login.js :

let DEVICES;
function a() {
  return DEVICES;
}

async function init() {
  try {
    const __devices = await _db_get_devices();
    DEVICES = new DeviceCollection(__devices);
    console.log(a()) <-- **Returns the object correctly**
  } finally {
    console.log("Login Initialised!");
  }
}

module.exports = { init, a }

Below is the code that is having issues:

App.js

const Login = require('./func/Login');

Login.init() <-- **runs init function no issues**

console.log(Login.a()); <-- **returns undefined**

I have figured that its something to do with async but that is why i setup a function to call it later so not sure if there is a better method to calling the variable when its set.

Answer 1

init is an async function, so following statement

console.log(Login.a())

will run before init function has executed completely. Hence you get undefined because DEVICES isn't initialized yet.

You can return DEVICES from the init function and call init function as shown below

Login.init()
  .then(data => console.log(data))    // log the return value of init function
  .catch(error => console.log(error);

or you could call function a after init function has executed completely

Login.init()
  .then(() => console.log(Login.a()))
  .catch(error => console.log(error);