Javascript
JavaScript is a high-level, interpreted programming language that makes websites interactive and dynamic. It 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.
Dynamic means Systems or pages that adjust, react, or are generated in real-time based on user input, rather than staying exactly the same for every visitor.
A versatile language is not trapped in just one job. It can be used across completely different tech industries.JavaScript is the ultimate example of a versatile language:
On Web Browsers: It runs animations, dropdown menus, and pop-ups.
On Servers: Using Node.js, it can manage databases and backend logic.
On Mobile: Using frameworks like React Native, it can build iPhone and Android apps.
On Desktops: Using Electron, it can build desktop apps like VS Code or Discord.**
Latest Version of Javascript
The current JavaScript version is ES2025.JavaScript was invented by Brendan Eich in 1995 and became an ECMA standard in 1997.The first ECMAScript versions were abbreviated by numbers. (ES1, ES2, ES3, ES5, ES6).From 2016, versions are named by year (ECMAScript 2016, 2017, 2018, ..., 2025).ECMA stands for European Computer Manufacturers Association. ECMAScript is the official name of the JavaScript standard.ECMAScript (often referred to as ES) is the official standardized specification for scripting languages like JavaScript. It sets the universal rules, syntax, and core features that a programming language must follow, ensuring consistent behavior across different web browsers and devices.
Compiler and Interpreter
A compiler and an interpreter are both tools that translate human-readable source code into machine-executable binary code. The primary difference is timing: a compiler translates the entire program before execution, while an interpreter translates and executes it line-by-line during runtime.
Data
Data is the Collection of information or values stored in computer memory that your program manipulates. A data type is a classification that tells the interpreter what kind of value a variable holds and how to interact with it.
Types of Data
A JavaScript variable can hold 8 types of data.7 Primitive Data Types and 1 Object Data Type.The Object data type can hold many different object types.
Number --->A number representing a numeric value.
Bigint---->A number representing a large integer.
String---->A text of characters enclosed in quotes.
Boolean--->A data type representing true or false,
Undefined--->A variable with no assigned value.
Null-------->A value representing object absence.
Symbol------->A unique primitive identifier(TBD).
Object------->A collection of key-value pairs of data(TBD).
The JavaScript Number data type has a fixed size of 64 bits (8 bytes).
Datatype Checking
A data type in a programming language refers to a characteristic that defines the nature of the value that a data element has. Some common examples include string, integer, character, and boolean.Every programming language has a system of checking that values have been assigned their correct types, which is known as type checking.There are two categories of type checking implemented in most programming languages, static and dynamic:
Variables
A variable is a named container in memory used to store data. It acts as a label for a value (like a number, text, or list) so the program can reference and manipulate it later.
Four Ways to Declare Varibales in Javascript
Declaration: Naming the container (e.g., score, username).
Assignment: Storing a specific piece of data inside it using an operator like =.
Older JavaScript
- Using var (Not Recommended)
- Automatically (Not Recommended)
Modern JavaScript
- Using let
- Using const
Examples using var
var age = 21;
var age = 22; // Redeclare ✓
age = 23; // Reinitialize ✓
Examples using let
let age = 21;
let age = 22; // Error ✗
age = 22; // Reinitialize ✓
Examples using const
const age = 21;
const age = 22; // Error ✗
age = 22; // Error ✗
Redeclaration
Creating the same variable again using the same name.
var age = 21;
var age = 22; // Redeclaration allowed
Reinitialization
Changing the value of an existing variable.
let age = 21;
age = 22; // Reinitialization allowed
References
https://www.geeksforgeeks.org/javascript/introduction-to-javascript/
https://www.w3schools.com/js/js_versions.asp
https://www.w3schools.com/js/js_datatypes.asp
https://www.w3schools.com/js/js_variables.asp
https://www.baeldung.com/cs/statically-vs-dynamically-typed-languages
Top comments (4)
Nice
Thank you!
Good and informative about the versions and its old names and their differences.Easy to understand this blog.👍️
Thanks!!