일부 JS.

JS has provided the date object and its methods which can be used to manipulate dates in our app. Out of those, there is a method called getDate() which returns the date. There have been times when I was required the number of days of a month. It can be done by using

new Date(2022,month,0).getDate()

0 here tells JS to give number of days of month previous to what we have specified. month here is a digit and months are 0 indexed in JS. So if I want to check number of days in Feb 2022, i call it like

new Date(2022,2,0).getDate()

Here 2 works because I want month previous to March. So when you read it, it aligns with our notion of addressing months as 1-indexed. Hence, its easier to remember.

Now, how does JS execute in the browser. JS is an interpreted language. This does not mean it does not get compiled. It gets compiled during the runtime unlike languages like C++ that are compiled well before execution. This Just in Time compilation is done by the JS engine. Apart from this, browser provides APIs like DOM, AJAX etc. You might not know this but console is also an API and it is not part of JS. In case of console object, it's easier to understand the program flow because it is not an async API. But what happens when an async task is performed. Let's say we have an async task of fetching some data and we are using fetch API.

fetch("https://rickandmortyapi.com/api/character?page=1", {
  method: "GET"
})
  .then((res) => res.json()) //callback function to convert response stream to JSON 
  .then((data) => console.log(data.results));