How it works...

By looking at the order of the log messages, you can clearly see the order of operations. First, the initial log is executed. Next, the promise is created with an executor method. The executor method takes resolve as an argument. The resolve function fulfills the promise.

Promises adhere to an interface named thenable. This means that we can chain then callbacks. The callback we attached with this method is executed after the resolve function is called. This function executes asynchronously (not immediately after the Promise has been resolved).

Finally, there is a log after the promise has been created.

The order the logs messages appear reveals the asynchronous nature of the code. All of the logs are seen in the order they appear in the code, except the Finished promise message. That function is executed asynchronously after the main function has exited!

We'll be looking more at resolve, then, and other parts of the promise API in later recipes in this chapter.