Promises
A promise is commonly defined as a proxy for a value that will eventually become available Asynchronous functions use promise behind the scenes, so understanding how promises work is fundamental to understanding how “async” and “await” works. Once a promise has been called, it will start in a pending state. This means that the calling function continues executing, while the promise is pending until it resolves, giving the calling function whatever data was being requested.
Creating a Promise: The Promise API exposes a Promise constructor, which you initialize using newPromise().
Using resolve() and reject(), we can communicate back to the caller what the resulting Promise state was, and what to do with it.
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