Get Twitter Account followers using API and Google Apps Script

I am trying to get the list of Twitter followers of a specific Twitter user using Google Apps Script. I found many sources:

> Source 1
Source 2
Source 3

but unable to create a link with my requirement. I have following code snippet:

function getFollowers(){

  var twitterKeys = {
    TWITTER_CONSUMER_KEY: '###',
    TWITTER_CONSUMER_SECRET: '###',
    TWITTER_ACCESS_TOKEN: '###',
    TWITTER_ACCESS_SECRET: '###',
  };

  var username = 'Example name'
  var props = PropertiesService.getUserProperties();
  props.setProperties(twitterKeys);
  var url = `https://api.twitter.com/2/users/${username}/followers`

  var options = {
    method: 'GET',
    headers: {
      api:twitterKeys
    },
    muteHttpExceptions: true
  };
  
  var response = UrlFetchApp.fetch(url, options);
  var json = JSON.parse(response.getContentText());
  
  console.log(json)   
}

On runs, it shows following output:

> { "title": "Unauthorized", "type": "about:blank", "status": 401,
> "detail": "Unauthorized" }

Any advice would be much appreciated to resolve it and get Twitter followers of a specific Twitter user.

The Twitter API relatively recently upgraded from version 1.1 to version 2, so a lot of the examples you'll find online are probably outdated.

Based on the URL, looks like you are using API v2, and it looks like the only thing you can do on the free version of API v2 is create/delete tweets and get information about your own account. You can see the endpoints that you have access to across tiers here (expand the cards to see the full endpoint).

If you do opt into the paid tiers (Basic is probably sufficient if all you need is individual user metrics), and access an endpoint that you are authorized to, the following code should work for you:

function getFollowers(){
  var username = 'Example name'
  var url = `https://api.twitter.com/2/users/by/${username}`

  var options = {
    method: 'GET',
    headers: {
      'Authorization': `Bearer: ${BEARER_TOKEN}` // Get this token from the twitter dev portal
    },
    muteHttpExceptions: true
  };
  
  var response = UrlFetchApp.fetch(url, options);
  var json = JSON.parse(response.getContentText());
  var userData = json.data;
  
  console.log(userData)
}

(I haven't tried this code, just cobbled it together from the docs here and here.