The console.log() method outputs a message to the web console. Read the tutorial and learn the simplest method of putting a single or multiple styles to it.
How Does the Access-Control-Allow-Origin Header Work
Read this tutorial and learn about how the Access-Control-Allow-Origin response header works. Also, read about CORS, the origin, and non-simple requests.
How the Keyword “this” Works
How to Access the Correct “this” Inside a Callback
How to Add a Class to a Given Element