JavaScript Essentials 1 ✅

JavaScript as an interpreted language

If we run a code written in JavaScript in a web browser, as it is happening, such as after loading the page we are currently reading (yes, yes, there are elements written in JavaScript on this page too), the interpreter will be the JavaScript engine built into the browser.
Node.js is also an interpreter, but installed independently of browsers as an environment in the computer's operating system (it can be macOS, Windows, or Linux). Using node.js allows you to write programs in JavaScript that will, for example, turn your computer into a server.
Most modern JavaScript engines use the Just In Time Compilation technique (JIT Compilation). This technique consists of compiling code fragments during the execution of the program (more than a single instruction) and allows you to increase its performance.
Like most interpreted languages, it is also a high-level language (i.e. relatively easy to understand for people and separating us from the hardware details).

History of JavaScript

Back in the early 90s, all web pages were static. Things changed in 1995 when the Netscape corporation hired Brendan Eich, and tasked him to develop a new language for their product, the Netscape Navigator web browser. The new language was called LiveScript, but soon after its name was changed to JavaScript. Its main task was to add dynamics to websites, which would allow, for example, for more complex interaction with the user. And so the career of JavaScript began.

Client side usually refer to front end while server-side is refer to back end
Client side → The code to be executed is loaded together with the page in the browser, on the user's side, and the interpreter which is a part of the web browser allows for its execution.
Server side → These programs are executed on servers, processing data (e.g. from databases), which after processing will be available on the client side.
The flexibility of this language and its relative simplicity have made it much more applicable.

var	let	const
- allow re-declare a varible	- prevent declarinng another varible with same name	- prevent declarinng another varible with same name
- can be re-assign value	- can be re-assign value	- value is initialize simultaneously when declaring the variable

cannot change the value | | - scope of the variable. become local if declare inside functions. | - scope of variable is depend on where it initialize (global or local) | - scope of variable is depend on where it initialize (global or local) | | | | |