This is a working code for Bitly using v4 API to shorten a long URL. You can also create a copy of this sheet and bulk create bitly links using the function bitlyShortenUrl
in the 3rd column- https://docs.google.com/spreadsheets/d/1TS-aQcDu3rRv-LexEoIqDiX0ydv69ijkXQP-nuQdBz4/edit#gid=0
function bitlyShortenUrl(longLink, accessToken) {
var form = {
"domain": "bit.ly",
"long_url": longLink
};
var url = "https://api-ssl.bitly.com/v4/shorten";
var options = {
"headers": { Authorization: `Bearer ${accessToken}` },
"method": "POST",
"contentType" : "application/json",
"payload": JSON.stringify(form)
};
var response = UrlFetchApp.fetch(url, options);
var responseParsed = JSON.parse(response.getContentText());
return(responseParsed["link"]);
}
PS: Bitly access token details given here https://support.bitly.com/hc/en-us/articles/230647907-How-do-I-generate-an-OAuth-access-token-for-the-Bitly-API-