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Annapoorani Kadhiravan
Annapoorani Kadhiravan

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Learning about JavaScript/ECMA Script

#webdev #javascript #beginners #programming

What is JavaScript and current version?

JavaScript (JS) is one of the most widely used programming languages in web development. It is used to create interactive and dynamic web pages.

Examples:

  • Button click actions
  • Form validation
  • Animations
  • Web applications
  • Real-time updates

Today, JavaScript is used not only for websites but also for backend development and mobile applications.

JavaScript is a versatile, dynamically typed programming language that brings life to web pages by making them interactive. It is used for building interactive web applications and supports both client-side and server-side development.

  • Interpreted language: Code is executed line by line.
  • Dynamically typed: Variable types are determined at runtime.

JavaScript versions are called ECMAScript versions (ES1, ES5, ES6, ES2020, etc.)

HISTORY OF JAVASCRIPT

How JavaScript Started

In May 1995, JavaScript was created by Brendan Eich at Netscape.

Interesting fact: JavaScript was developed in just 10 days.

JavaScript went through multiple names:

Mocha
↓
LiveScript
↓
JavaScript

What makes JavaScript unique

JavaScript is a unique and essential programming language with several key features and capabilities that make it distinguished from the other languages. The following are the reasons why JavaScript is unique.

  1. Client-side dominance
  2. Full-stack development
  3. Asynchronous programming
  4. Event-driven programming
  5. Interpretation
  6. Just-in-time compilation
  7. Frameworks and Libraries
  8. Active Community

ADVANTAGES AND DISADVANTAGES OF JS

The advantages of using JavaScript on your website are that it:

  1. Works with all major browsers and devices
  2. Enables interactive features like menus, sliders, tabs, and forms
  3. Is versatile enough for everything from simple animations to fully dynamic experiences
  4. Easily connects with other marketing tools and platforms (like analytics, chat, or email widgets)

The downsides of using JavaScript on your website are that it:

  1. Can sometimes hide important content (like page titles, descriptions, or links) from search engines if those elements depend on JavaScript to load. This can hurt how your site shows up in search results.
  2. Slows down page speed, especially if scripts are large or poorly optimized
  3. May behave differently across some browsers, particularly older ones
  4. Can create security risks if you use untrusted scripts or plugins—JavaScript runs automatically in the browser

JavaScript Ecosystem

Many technologies are built using JavaScript.

Examples:

  • React JS → Frontend UI library
  • Angular → Frontend framework
  • Node.js → Backend runtime environment

These technologies extend JavaScript for different application development purposes.

How Computers Understand Code

Computers understand only binary language:

0 and 1
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Programming languages must be translated into machine language.

Two common translation approaches:

1. Interpreter

Converts code line by line.

Example:

JavaScript → Interpreter → Machine Language
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Advantages:

  • Easier debugging
  • Executes immediately

2. Compiler

Converts the entire program at once.

Example:

Source Code → Compiler → Machine Code
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Advantages:

  • Faster execution after compilation

Note:
Modern JavaScript engines (like V8) use both interpretation and compilation internally for performance.

Why JS is an Interpreter Language?

JavaScript is primarily considered an interpreted language because it is sent to the browser as raw text and translated into machine code "line-by-line" at runtime, making it highly flexible. However, modern engines use a hybrid approach to improve performance.

What is Programming?

Programming means:

Giving instructions to a computer to perform specific tasks.

Example:

Open browser
Display website
Store user data
Calculate result
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Applications help businesses manage and process huge amounts of data efficiently.

JavaScript Data Types

Data types define what type of value is stored.

1. Number

Stores normal numeric values.

Example:

let age = 25;
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2. BigInt

Stores extremely large numbers.

Example:

let population = 12345678901234567890n;
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Unlike Number, BigInt supports values larger than the safe integer range.

3. Boolean

Stores true or false.

Example:

let isLoggedIn = true;
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4. String

Stores text values.

Example:

let name = "Annu";
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Understanding Bytes and Bits 

1 Byte = 8 Bits
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Binary uses only:

0 and 1
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Example:

2^8 = 256 possible combinations
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Signed values can represent:

-128 to 127
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JavaScript Number uses 64-bit floating point representation.

Types of Programming Languages

1. Statically Typed Language

Data type must be declared.

Example (Java):

int age = 10;
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Rules:

  • Data type mandatory
  • Syntax strict

2. Dynamically Typed Language

Data type is automatically determined.

Example (JavaScript):

let age = 10;
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JavaScript decides the type internally.

Variables in JavaScript

Variable:
A named storage location whose value may change.

Example:

let name = "Annu";
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Structure:

Variable = Value
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Example:

name = "Annu"
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  • name → Variable
  • = → Assignment Operator
  • "Annu" → Data

Semicolon (;) is optional in JavaScript but considered a good practice.

Ways to Declare Variables

1. Without Keyword (Not Recommended) 

name = "Annu";
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Problem:

  • Can create accidental global variables.

2. Using var 

var name = "Annu";
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Problem:

var name = "Apple";
var name = "Orange";
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Redeclaration is allowed.

Not preferred in modern JavaScript.

3. Using let (ES6) 

let age = 16;
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Features:

  • Cannot redeclare in same scope
  • Value can change

Example:

let age = 15;
age = 20;
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Valid.

4. Using const 

const price = 99;
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Features:

  • Cannot redeclare
  • Cannot reassign

Example:

const price = 99;
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JavaScript Versions

JavaScript evolves through ECMAScript versions.

Examples:

ES5
ES6
ES7
ES8
ES9
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What is ECMA?

  • ECMA stands for the European Computer Manufacturers Association.
  • It was founded in 1961 as a non-profit industry association to develop standards for information technology, electronics, and programming languages.
  • ECMA is now officially known as ECMA International to reflect its global reach.
  • ECMAScript is the standard specification that defines how JavaScript should work.

ES means:

ECMAScript

It is the official standard specification for JavaScript.

Example:

ES6 (2015) introduced:

  • let
  • const
  • Arrow functions
  • Classes
  • Modules

JavaScript follows ECMAScript standards.

References :

https://www.w3schools.com/whatis/whatis_js.asp
https://www.semrush.com/blog/javascript/
https://www.geeksforgeeks.org/javascript/introduction-to-javascript/
https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/Scripting/What_is_JavaScript
https://mvjce.edu.in/blog/evolution-of-javascript/

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