state: pending -> fulfilled or rejected
Producer vs Consumer
when new Promise is created, the executor runs automatically.
we can make some delay.
JS — Callback hell
Callback Hell what is callback hell? Callback Hell, also known as Pyramid of Doom, is an anti-pattern seen in code of asynchronous programming. It is a slang term used to describe and unwieldy number of nested “if” statements or functions. below picture is also example of callback hell