[JAVASCRIPT] What is the difference between let, var, const, and where to use it.

let /const

Scope: let and const have block scope which means they are accessible within the block in which they are declared

Reassignment: let can be reassigned with a new value but in terms of const it cannot be reassigned once declare

function letConstEx(){
 let x = 5
 const y =6
 if(true){
     let z = 6;
     console.log(x)// able to get value of its block scope is start of the fucntion still end
     console.log(y)
 }
 console.log(z) // ReferenceError: z is not defined as its block scope is if condition
}
letConstEx()

Var

Scope: It has a functional scope which means they are accessible within the function where they are declared

Reassignment: the Value of var can be declared again and again inside the same function.

function even() {
    var x = 2; // declare inside a  even function
    var y = 3;
    if(x ===2 ){
        var x = 5//  reassignment of var
        console.log(x)// able to get the value 
    }
    else{
        console.log(y)
    }
}
even()

In general, it's recommended to use const for values that are not meant to be reassigned, and let for values that are meant to change. var should be avoided in modern JavaScript.

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