1. Variables: var , let , and const

Variables allow us to store data.

JavaScript provides three ways to declare variables:

var

let

const

var

var is the older way of declaring variables.

var framework = " React " ;

console . log ( framework ); // React

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However, var has some important problems.

For example, it is function-scoped rather than block-scoped.

if ( true ) { var framework = " React " ; }

console . log ( framework ); // React

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The variable escapes the if block.

This behavior can create unexpected bugs.

let

let allows you to declare variables that can be reassigned.

let age = 25 ;

age = 26 ;

console . log ( age ); // 26

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Unlike var , let is block-scoped.

if ( true ) { let framework = " React " ; }

console .…