Pre-request script for authentication in Postman requests

pre-request.js

const username = pm.environment.get("authUser");
const password = pm.environment.get("authPass")

const options = {
  url:  'https://api.be/v1/auth/token', 
  method: 'POST',
  header: {
    'Authorization': 'Basic ' + btoa(username + ':' + password)
  }
};

pm.sendRequest(options, function (err, response) {
    const responseJson = response.json();
    if (responseJson.access_token) {
       pm.environment.set("authToken", responseJson.access_token);
       pm.globals.set("authToken", responseJson.access_token);
    }
});