It all started when I kept getting the No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access. error and the workaround didn't seem interesting to me.
When I made the Today in Google Doodles history, I was making ajax requests to the https://www.google.com/doodles/json/:year/:month Google API.
After observing the networks requests that https://www.google.com/doodles makes to fetch their doodles, I figured out that that's where they were sending their requests.
As it turns out, for some reason, the https://www.google.com/doodles/json/:year/:month api is not 'public'. It is publicly accessible because anyone can make a request to it with no credentials and retrieve google doodles for a specific month in any given year.
But making browser client ajax requests failed (I used JQuery .ajax() and the fetch() JS API). Since Google didn't make that api with the intent of making it public, they didn't specify the Access-Control-Allow-Origin header on their servers to allow any browser requests. In other words, browsers block any ajax requests to it because those requests are not coming from the same origin that the api is on.
I found this MDN page to be helpful to understand more about Cross-Origin Resource Sharing (CORS).
One way of getting around the CORS violation error (in Google Chrome) is adding the Allow-Control-Allow-Origin: * extension to Chrome and enabling it.
But telling people to check out your new cool page and telling them to first install an extension was an overkill. So I just created a simple CORS-enabled node.js & ExpressJS proxy server https://google-doodles.herokuapp.com hosted on Heroku. My Today in Google Doodles history page sends its GET doodles requests to the proxy server via /doodles/:year/:month route. Then the proxy server makes fetch requests to the good 'ole https://www.google.com/doodles/json/:year/:month API and returns the result back to the client.
I learned how to enable CORS on a node.js & expressJS server from here
Easy Day!