Google Apps Script/URLFetchApp and using returned data - api

Question

I am very new to this, so please bear with me-- I have currently have an operational google apps script on the backend of a google sheet that is generated from Google Form answers. I am essentially setting up a ticket form in google forms that will trigger the data in the corresponding sheet to be sent via api call to our ticketing system. It works great, but I am trying to optimize it currently. The goal is to take the json response I get using:
Logger.log(response.getContentText());
which provides me the following info:
Aug 9, 2020, 11:44:40 AM Info {"_url":"https://testticketingsystem.com/REST/2.0/ticket/123456","type":"ticket","id":"123456"}
and send another API call to send data to that new ticket.
Here's a code snippet:
var payload = {
"Subject": String(su),
"Content": String(as),
"Requestor": String(em),
"Queue": String(qu),
"CustomFields": {"CustomField1": String(vn), "CustomField2": String(vb), "CustomField3":
String(vg), "CustomField4": String(av), "CustomField5": String(ov), "CustomField6":
String(sd)}
}
var options = {
'method': 'post',
"contentType" : "application/json",
'payload': JSON.stringify(payload),
'muteHttpExceptions': true
}
var url = "https://testticketingsystem.com/REST/2.0/ticket?token=****************";
var response = UrlFetchApp.fetch(url,options);
Logger.log(response.getContentText());
} catch (error) {
Logger.log(error.toString());
}
}
After the ticket is created, how do I script the use of that ID number as a variable into my next api call?
Thank you!

Answer 1

UrlFetchApp.fetch returns a HTTPResponse, and if you expect JSON then you should be able to just use JSON.parse() to create an object from the text. (The JSON object is a standard JavaScript global object like Math; it is not Google Apps Script specific.)
If all goes well, you should just be able to use
var response = UrlFetchApp.fetch(url,options);
var data = JSON.parse(response.getContentText());
var id = data.id;
and then use that id for your next fetch().
Notes
If your literal response is indeed
Aug 9, 2020, 11:44:40 AM Info {"_url":"https://testticketingsystem.com/REST/2.0/ticket/123456","type":"ticket","id":"123456"}
you will run into trouble as everything until the { is invalid JSON (use a linter if you need to check yourself). But I'm assuming that was added by the console when you logged JSON, and not in the actual response itself.
JSON.parse() throws an error with invalid JSON, so you can use try/catch if needed.
You can also check the headers before you try to JSON.parse().
Here's an example that checks and handles issues, should they arise.
var type = response.getHeaders()["Content-Type"];
var text = response.getContentText();
if (type === "application/json") {
try {
var data = JSON.parse(text);
} catch (error) {
return Logger.log("Invalid JSON: " + response.getContentText(text));
}
} else {
return Logger.log("expected JSON, but got response of type: " + type);
}
// if we get to this line, data is an object we can use