Variables and Scope | JavaScript Basics ( before Typescript , node js ) - 4

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JavaScript - Variables - Scope
🟪Contents -Topics covered in this video :
➡️ What is Variable ?
➡️ Keywords to declare variable
➡️ Rules for naming variable
➡️ What is scope
➡️ global scope vs local scope
➡️ Problem with “var” keyword ?
➡️ why let and const in ES6

In this tutorial you will learn how to use variable in javascript in English .You can learn how to store any value in variable and then reuse it as many times in javascript.
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Previous Video :
🔵 Primitive Type vs Reference Type | JavaScript Basics ( before Typescript , node js ) - 1

🔵 null vs undefined | variable life cycle | JavaScript Basics ( before Typescript , node js ) - 2

🔵 === vs == | Which one is better? | JavaScript Basics ( before Typescript , node js ) - 3
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What is Variable ?
JavaScript variables are containers for storing data values.Before the advent of ES6, var declarations ruled. There are issues associated with variables declared with var, though. That is why it was necessary for new ways to declare variables to emerge.

ES2015 (or ES6) introduced two new ways to create variables, let and const. But before we actually dive into the differences between var, let, and const, there are some prerequisites you need to know first.

What is Scope ?
Scope in JavaScript defines accessibility of variables, objects and functions. One advantage is that scope provides some level of security to your code.Variables defined inside a function are in local scope while variables defined outside of a function are in the global scope.

The scope is a policy that manages the accessibility of variables.

Block Scope : In Javascript you can define a code block using curly braces i.e {}.

Function scope : In Javascript you limit the scope of a variable by defining it within a function.

In effect if a variable is defined with keyword var, Javascript does not recognize the {} as the scope delimiter. Instead the variable must be enclosed within a “function” to limit its scope to that function.
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Reference Vs Value In JavaScript
-TypeScript is an open-source programming language developed and maintained by Microsoft. It is a strict syntactical superset of JavaScript, and adds optional static typing to the language. In this typescript tutorial for beginners, we go over the fundamental concepts like variable declarations, variable types, functions, interfaces, classes and access modifiers.

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What is JavaScript ?
JavaScript was initially created to “make web pages alive”.
JavaScript is an open and cross platform, dynamic computer programming language which is developed to implement complex features on web pages . It is a scripting language , which is used on both client and server side. JavaScript is the language of web development.

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