Functions in Nodejs - node.js

Question

I am new to Nodejs and am trying to figure out why I cannot pass the returned value of my function into my function when I call it. Here is my code:
const SpotifyWebApi = require('spotify-web-api-node');
const http = require("http");
const request = require('request');
const querystring = require('querystring');
const { post } = require('request');
const express = require('express');
const { response } = require('express');
const https = require('follow-redirects').https;
//sets express server vars
const app = express()
const port = 8080
app.get('/', (req, res) => {
res.send('Server Connected')
})
app.listen(port, () => {
console.log(`Now serving on ${port} at ${process.env.URI} `)
})
require('dotenv').config();
//authenticate to SpotifyAPI
var spotifyApi = new SpotifyWebApi({
clientId: process.env.CLIENT_ID,
clientSecret: process.env.SECRET_ID,
redirectUri: process.env.URI,
});
const scope = 'user-read-private user-read-email ';
const authUrl = 'https://accounts.spotify.com/api/token?grant_type=client_credentials';
//Headers needed to auth to SpotifyAPI for Bearer token
const tokenHeaders = {
'Authorization': process.env.ACCESSTOKEN,
'Content-Type': 'application/x-www-form-urlencoded',
};
//spotify Auth Payload
const options = {
'method': 'POST',
'url': authUrl,
'headers': tokenHeaders
};
function accessTokenAuth(bearerToken){
request(options, (error, response) => {
if (error) throw new Error(error);
const accessTokenBody = response.body;
// console.log(accessTokenBody)
// console.log(request)
const obj = JSON.parse(accessTokenBody);
const bearerToken = ("Bearer " + obj.access_token); //add this bearerAuth part to a function to make it repeatable. Times out in 3600???
// console.log(bearerToken);
return bearerToken;
});
}
//Add first playlists request using the bearer token
accessTokenAuth(bearerToken);
In the function "accessTokenAuth" I create a series of calls that essentially posts data from the above dictionaries into a function that then sends the data to the URL to receive a token back. My question is this, at the bottom of the function when I return "bearerToken", how come I cannot pass "bearerToken" into the function when I call it on line 67. Also, when I comment out calling the function and just run the program it prints out the "bearerToken" when I console.log it in the function. Why is this possible? Aren't you not able to access the function unless it is called?
Thank you!