JavaScript 101 - Introduction to JavaScript

Introduction To JavaScript

22 September, 2022

Contributors

Gaurav Sharma

@gsharma010

What is JavaScript ?

JavaScript is a high-level prototype-based object oriented Multiparadigm, interpreted or just in time compilated dynamic, single Treaded, garbage collected programming language with first-class functions and a non-blocking event loop concurrency module.

Don't worry 🤯🤯.

Let's break above definition into points. - High-level - Garbage-Collection - Interpreted or just in time compiled - Multi-paradigm - Prototype-based object-oriented approach - First class functions - Dynamic - Single-Threaded - Non-blocking event loop

1️⃣ JavaScript is High-Level

🟡 Every program that runs on our computer needs some hardware resources such as memory and the cpu to do it's work.

🟡 There are low level languages like C where we have tom manually manage these resources.

🟡 On the other side we have high level languages like python and JavaScript where we do not have to manage resources at all.

🟡 Because these languages have so called abstractions that take all of the work away from us.

2️⃣ JavaScript is Garbage-Collection

🟡It is basically an algorithm inside the JavaScript engine that removes old, unused objects from the computer memory

🟡JavaScript cleans our memory from time to time so that we don't have to do it manually in our code

3️⃣ JavaScript is interpreted or Just-in-time compiled

🟡Computer processor ultimately understands 0 or 1 every single program needs to be written in binary language which is also called machine code.

🟡That is not practical to right that's why we write human-readable code.

🟡Like JavaScript which is an abstraction over machine code.

🟡But this code eventually needs to be translated to machine code and that step can be either compiling or interpreting.

🟡Above step is necessary in every single programming language.

🟡Because no one write machine code manually. In case of JavaScript This happens inside the JavaScript engine.

4️⃣ Multi-paradigm

🟡In programming a paradigm is an approach overall mindset of structuring our code. Which will ultimately direct the coding style and technique in a project that uses a certain paradigm.

🟡Some popular programming paradigm are:- - Procedural Programming - Object-oriented programming (OOP) - Functional Programming

5️⃣ Prototype-based object-oriented approach

🟡All most everything in JavaScript is an object except of primitive values.

🟡But arrays, for example are just object.

🟡Now, have you ever wondered why we can create an array and then use the push method on it

🟡It's because of "prototypal inheritance". Basically we create arrays from an array blueprint which is like template and this is called the prototype.

🟡I will create a separate thread on prototypal inheritance.

6️⃣ First class functions

🟡In a language with first-class functions, functions are simply treated as variables. We can pass them into other functions, and return them from functions.

🟡Which means functions are treated as regular variables

🟡So, we can pass functions into other functions and we can even return functions from functions.

7️⃣ Dynamic

🟡JavaScript is a dynamic language which means dynamically-typed language

🟡In JavaScript we don't assign data types to variables, instead they only become known when the JavaScript engine executes our code.

8️⃣ Single-Threaded

🟡Before know what is single threaded we need to know about the "Concurrency Model"

🟡Well "Concurrency Model" is a fancy term that means how the JavaScript engine handles multiple tasks happening at the same time.

🟡JavaScript itself runs in one single-thread which means it can only do on thing at a time and therefore we need a way of handling multiple things at the same time.

🟡By the way in computing a thread is like a set of instructions that is executed in computer's CPU

🟡So basically, the thread is where our code is actually executed in a machine's processor.

🟡But what if there is a long running task like fetching data from a remote server.

🟡Well it sounds like that would block the single thread where the code is running right.

🟡But we don't want that. what we want is

9️⃣ Non-blocking event loop

🟡Non-blocking behavior and how do we achieve that. Well by using a so-called event loop. The event loop takes long-running tasks, executes in the background and put's them back in the main thread

🟡This is in a nutshell JavaScript's non-blocking event loop concurrency model with a single thread