Postman Prerequest to get the oauth token and send it with actual request

pm-Prereq-token-Auth.js

getToken=true;

var envlevel=pm.environment.get('env');
var userName='';
var password='';
var auth_audience='';
var auth_scope='';

//console.log(envlevel);
switch(envlevel){
    case 'local':
        userName=pm.variables.get("auth_local_userName");
        password=pm.variables.get('auth_local_password');
        auth_scope=pm.variables.get('auth_local_scope');
        auth_audience=pm.variables.get('auth_local_audience');
        break;
    case 'dev':
        userName=pm.variables.get("auth_dev_userName");
        password=pm.variables.get('auth_dev_password');
        auth_scope=pm.variables.get('auth_dev_scope');
        auth_audience=pm.variables.get('auth_dev_audience');
        break;
    case 'test':
        userName=pm.variables.get("auth_test_userName");
        password=pm.variables.get('auth_test_password');
        auth_scope=pm.variables.get('auth_test_scope');
        auth_audience=pm.variables.get('auth_test_audience');
        break;
    case 'beta':
        userName=pm.variables.get("auth_beta_userName");
        password=pm.variables.get('auth_beta_password');
        auth_scope=pm.variables.get('auth_beta_scope');
        auth_audience=pm.variables.get('auth_beta_audience');
        break;
    case 'prod':
        userName=pm.variables.get("auth_prod_userName");
        password=pm.variables.get('auth_prod_password');
        auth_scope=pm.variables.get('auth_prod_scope');
        auth_audience=pm.variables.get('auth_prod_audience');
        break;
}

//console.log(userName);
//console.log(password);
//console.log(auth_scope);
//console.log(auth_audience);

var CryptoJS = require("crypto-js");
var combinedCredentials=userName+":"+password;
var credentialsRaw=CryptoJS.enc.Utf8.parse(combinedCredentials);
var base64EncodedCredentials= CryptoJS.enc.Base64.stringify(credentialsRaw);

//console.log(combinedCredentials);
//console.log(base64EncodedCredentials);


const postTokenRequest = {
  url: pm.environment.get('auth_token_url')+'?grant_type='
  +pm.environment.get('auth_grant_type')
  +"&aud="+auth_audience
  +"&scope="+auth_scope,
  method: 'POST',
  header: {
      'Content-Type':'application/json',
      'Authorization':'Basic '+base64EncodedCredentials
      
  }
};


if (!pm.variables.get('tokenExpiry') || 
    !pm.variables.get('currentAccessToken')) {
    console.log('Token or expiry date are missing');
} else if (pm.variables.get('tokenExpiry') <= (new Date()).getTime()) {
    console.log('Token is expired');
} else {
    getToken = false;
    console.log('Token and expiry date are all good');
}

if (getToken === true) {
    pm.sendRequest(postTokenRequest, function (err, res) {
    console.log(err ? err : res.json());
        if (err === null) {
            console.log('Saving the token and expiry date');
            var responseJson = res.json();
            pm.variables.set('currentAccessToken', responseJson.access_token);
            //console.log("currentAccessToken: "+ pm.variables.get('currentAccessToken'));
    
            var expiryDate = new Date();
            expiryDate.setSeconds(expiryDate.getSeconds() + responseJson.expires_in);
            pm.variables.set('tokenExpiry', expiryDate.getTime());
            //console.log("tokenExpiry: "+pm.variables.get('tokenExpiry'));
        }
    });
}