A Simple Promise Library

I was having a hard time understanding how Javascript Promises work, so thought of implementing a simple version of it myself.

You can see it here Simple-Promise.

It should cover the basic use cases of promises.

People who are new to Javascript and are trying to learn about Promises might find it useful as it exposes some of the inner workings of the library.

I’d like to get feedback from others as well.

Is it of any use? How can it be improved in terms of implementation, documentation etc?