Answer: All APIs of Node.js library are aynchronous that is non-blocking. It essentially means a Node.js based server never waits for a API to return data. Server moves to next API after calling it and a notification mechanism of Events of Node.js helps server to get response from the previous API call.

Source: tutorialspoint.com

In this document I am using Sass's SCSS syntax. You can choose to use the indented syntax in sass, if you prefer it, it has no functional differences from the SCSS syntax.

For Less, I'm using the JavaScript version because this is what they suggest on the website. The ruby version may be different.