I wanted to share this because the first time that I needed to debug the backend I found just a bunch of discussions and URLs to articles but nothing clear/concrete on how to simply console.log() from the backend as you would do when using the developer tools if the browser.
You can console.log() your backend extremely easy.
Go to your Wix dashboard - settings - site monitoring.
There click the "OPEN" button. Once this is ready.
Using your live site run it, run from your frontend a promise that calls for a backend function, if the backend function contains a CONSOLE.LOG() this console will be displayed in the site monitoring as a JSON object.
this is site monitoring in action:
Then click on any of the logs:
The jsonPayload contains always your console.log() from the backend. And then keep in mind ALWAYS this message comes in an array, your console.log() is everything but the array. In this case "controller has been called from not submit" is a string that I wrote in my console.log(); as an argument of the log() method.
That is already stated in the Wix Support pages as shown here.
https://support.wix.com/en/article/corvid-testing-and-debugging-your-code#backend-code-http-functions-1
https://support.wix.com/en/article/corvid-testing-and-debugging-your-code#debugging-with-site-monitoring