What is JavaScript Brief Introduction | JavaScript Introduction in details | JavaScript Introduction History Syntax and Types

Introduction

JavaScript is a "Just In Time" compiled language

Which was made by Brendon Eich in 1995

At that time it was known as "Mocha"

And JavaScript is designated as the world's most popular programming language

There's a JavaScript engine in every browser which is responsible for

Running the JavaScript in that particular browser

JavaScript is like one of the World Wide Web technologies, for example HTML and CSS

Webpages used to be static before the JavaScript came into existence

But when JavaScript is introduced in any website, client side logic is enabled

And users can interact with those websites very effectively

Over 90% of the websites use JavaScript on the client sites

 

JS History

Before the JavaScript came into existence, the websites were static

And Brendan Eich realised that

It was really important to introduce a language like JavaScript on the client sites of browser

That's why he started working on JavaScript, along with NetScape

In 1995, there was a browser's war going on which included Microsoft and NetScape

NetScape used to tell the users to use the NetScape Navigator

And as usual Microsoft used to tell the users to use the Internet Explorer

Anyhow Internet Explorer became so infamous that Microsoft had to develop "Edge" for the users

There were allegations that Microsoft had reverse engineered Netscape and started working on a standard named "J Script"

But in 1997

The first version of ECMA was released

ECMA is a standard that ensures that during all the runtimes of JavaScript,

The behaviour of JavaScript remains predictable

This ensures that the same JavaScript code, in different browsers, behaves in a very similar manner

Extension of JavaScript can be {.js}, {.mjs} as well as {.cjs}

JavaScript was named "Live Script" in its Beta release but finally

It was named JavaScript

One of the reasons for this was, NetScape was one of the greatest supporters of JavaScript

And for the sake of marketing of Java, NetScape named this langugage as "JavaScript"

Java was a trending programming language at that time

Therefore Brendan Eich used to think that its the marketing ploy of NetScape

That they are naming the language "JavaScript" in reference to a very popular programming language "Java"

But finally it was named "JavaScript"

And till date, it still confuses the programmers

Java and JavaScript are totally different programming languages

In 2009, an amazing thing happened

Ryan Dahl introduced the V8 engine of Chrome, which was a JavaScript engine, into a C++ program

Then it became possible to run the JavaScript, even outside of browser and client sites

That is how Node.js was established and Node.js became a very popular runtime

Similar to this runtime, JavaScript can be run in many other runtimes, outside of browser

Because of this, people started using JavaScript outside of browser

Till 2018, millions of users started using Node.js

Not just that, the "Node Package Manager" of Node.js holds the maximum number of packages in this world

In 2015, a new version of JavaScript was introduced which was a major change

It was known as ES6

And a lot of major syntactical changes were introduced in this language

Some of them were: 1. ES6 modules; 2. Iterators; 3. For of Loops; 4. Python style generators; 5. Let and Const Keywords; 6. Promises; 7. Template Literals, and so on

So this was about the history of JavaScript, now let’s move towards the syntax

 

JS Syntax

And let’s learn about the syntax of JavaScript in more details

 

Console

Console has been provided in the JavaScript programming to lock the JavaScript in the browsers

Errors, warnings and custom messages of JavaScript is printed inside the Console

To print anything inside the Console of a browser, you can use "console.log()"

 

Comments

Comments are the text which are not parsed through JavaScript

Which means a valid code is not accepted by JavaScript

The syntax to write a Single Line Comment in JavaScript is somewhat like this

And to write a Multi-Line Comment, the syntax is somewhat like this

 

Variables in JS

You can declare a Variable using the keywords "Var", "Let" and "Const"

If you are using the "Var" keyword then you can redeclare and change the Variables

If you use the "Let" keyword then you cannot redeclare the Variable

But you can update the variable like "Var"

But if you are using the "Cont" keyword then that is a constant

You can neither update the variable nor declare the variable

One more difference between Let and Var is that, the value of the variable initialized using "Var" is undefined

But the value of the variable initialized using "Let" is not undefined

 

Arithmetic Operators in JS

You can use the Arithmetic Operators in JavaScript in this way

 

Data Types in JS

There are two types of Data in JavaScript programming

1. Primitive values

2. Objects

Primitive values are those immutable data which is at the lowest level of this language

There are seven types of Primitive Datatypes in JavaScript which are present on your computer screen

 

JS Objects

You can make objects in JavaScript

In which you can write the key value pairs

And syntax to access the keys in object is somewhat like this

You can also change an object using a syntax just like this one

And you can also print an object using a syntax just like this one

You can also make Nested Objects which means you can put an object, inside an object, using a syntax like this one

 

Conditional Statements

You can use "If Else Conditionals" in JavaScript

You can put a condition inside "If" which is either true or false

If the condition is true, the code inside "If" will be executed

And if the condition is false, the code inside "Else" will be executed

The syntax to write "If-Else" is somewhat like this

You can write an "If-Else Ladder" in JavaScript in this way

 

Switch Case Statements

JavaScript also includes "Switch Case Statements" which are similar to conditionals

Which helps in running few cases which are based on the values of variable

The syntax of Switch Case in JavaScript is somewhat like this

 

Loops

There are many types of Loops in JavaScript

1. For Loops; 2. For Each Loops; 3. For Of Loops; 4. Do While Loops; 5. While Loops

The syntax for "For Loops" is somewhat like this

The syntax for "For Each Loops" is somewhat like this

And the syntax for "For of Loops", in JavaScript, is somewhat like this

"While Loops" in JavaScript can be made in this way

And "Do While Loop" in JavaScript can be written in this way

To separate your logic in JavaScript, you can write "Functions" using a syntax in this way

 

Functions in JS

You can call these Functions in this way

There is a concept of "Arrow Function" in JavaScript

According to which you can write the Functions, in JavaScript, in this way

This function includes a very convenient syntax

Along with this, there are some more differences between Arrow Function and Normal JavaScript Function

 

Events in JS

JavaScript also include "Events" which you can listen to,

Like when a user clicks on an element or any user defined custom event is fired

You can write a code in JavaScript which will be executed

You can see in this code, when you click the button it will print "Happy Birthday" on the console

 

Strings

You can make "Strings" in JavaScript using this syntax

The important methods and uses of "String", are present on yoour screen

Using Template Literals in JavaScript, you can imbed variables in a string

 

Template Literals

The syntax of Template Literals is somewhat like this

You can see here that you can print the variables directly into the string

There are few methods of "Numbers" in JavaScript, which are present on your screen

 

Arrays

You can use "Array" to make a collection of elements in JavaScript

And its syntax is somewhat like this

Few important methods of Array are present on your screen

"Date Object" in JavaScript helps you to represent the date

 

Type of Operator

Using the Type of Operators you can get to know the type of any variable

The syntax of Type of Operators if somewhat like this

 

Hoisting in JS

There is a concept of "Hosting" in JavaScript

In which the interpreter moves the Variables, Classes and Functions to the top of the Code

This work is done by the interpreter, before the code is executed

 

OOPS in JS

JavaScript is an object oriented programming language

And you can make the "Classes" in JavaScript in this way

In this way you can invoke the constructor

And in this way you can perform inheritance in JavaScript

There is a "THIS" keyword in JavaScript

Which is used to refer to the current object

If you write "This.Something" inside a class, "This" refers to the object that is being made

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