google-api-javascript-client | Google APIs Client Library for browser JavaScript , aka gapi | REST library

I'm reading this getting started document:

https://github.com/google/google-api-javascript-client/blob/master/docs/start.md

In Option1, the following code is written:

It's very nice that the gapi api is able to keep a user signed in but I would like to understand how it does it.

In the developer docs it states that

Then, if the user has already signed in, the GoogleAuth object restores the user's sign-in state from the previous session.

The only way I know of doing this is by using a refresh token which is insecure if stored on the client.

How does the gapi-api acheive this?

I would refer to the sources, but I don't think they are open.

Trying to understand how I should go about referencing the google apis for a static page web app. I am confused.

1. I am unsure where the complete documentation is as I have stumbled upon a few broken links in this repository already
2. These tutorial reference 2 different urls yet seem to be related to this repository

https://developers.google.com/identity/sign-in/web/reference#gapiauth2initparams

After upgrading to Mac OS X version 10.15.2 sign in to Google with the google-api-javascript-client library has stopped working for some users in Safari.

The Safari developer console and network tab doesn't really tell me much regarding what the issue is for that specific Safari version.

Using the Javascript client, I'm submitting a large number of requests to batchUpdate(). The code below was working perfectly until a few hours ago. I've tried reducing the number of requests as suggested here but that seems to make no difference. See below for the code I'm using, it's pretty simple. The template being copied is open so it should run assuming you put a client_id and api key in there.

This is Yet another error 403 on Google Sheets API. Um trying to read the data from a Spreadsheet and expose it on a website, using some custom HTML filters.

So, there is this question: Error 403 on Google Sheets API

Still, I cannot figure out what to do. I have setup my service account in the google cloud platform, granted it permissions to access my Spreadsheet - I have even made my SpreadSheet accessible via link (but that is restricted to emails from my organization, so it seems useless anyway). I've also activated domain-wide delegation for my service account - didn't make any difference at all. I'm pretty sure the issue is not related to a wrong key or some typo because, when I remove the access to the service email from the sheet, I steel get a 403 error, but it comes with a message saying the caller doesn't have access to that spreadsheet.

People keep mentioning OAuth, but I don't want to use that, since I'm intending to use a simple API access, as in this Google GitHub example. I'm using my business account, so there might be some issue related to that.

Here is the HTML (which I'm running from a simple HTTP server on python, not directly, given the fact the GAPI doesn't handle localhost/ sources very well):

API Discovery Service of BigQuery had worked well, but recently it suddenly returns error.

1. NG https://www.googleapis.com/discovery/v1/apis/bigquery/v2/rest?fields=kind
2. OK https://www.googleapis.com/discovery/v1/apis/bigquery/v2/rest
3. OK https://www.googleapis.com/discovery/v1/apis/discovery/v1/rest?fields=kind

Google's API Discovery Service has fields parameter. It works well in some api such as discovery (case 3), but doesn't work in bigquery (case 1).

From Google's API explorer and using Authorize requests using OAuth 2.0 as I want to on my SPA, I see a YOUR_API_KEY is somehow derived from a login and used in subsequent calls to: