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VAR vs.LET vs. CONST

var let const

var , let , const are containers helps to store data;
It can be named with alphanumeric chararcters;
first letter compulsorily alphabet not numeric or symbol.
It accept dollar symbol ($)alone.





 VAR vs.LET vs. CONST


var is not blockscope

let and const are blockscope

let can be undefined but const can't



var vs. let vs. const

var a = 10;
console.log(a) // a =10
 {
    var a = 20;
    console.log(a) // a=20
}
console.log(a)  // a =20;
var a = 30;
console.log(a) //a =30

let a = 10;
console.log(a) // a =10
 {
     let a = 20;
    console.log(a) // a=20
}
console.log(a)  // a =10;
let a = 30;     // Error - redeclaration of let a
console.log(a)


const a = 10;
console.log(a) // a =10
 {
     const a = 20;
    console.log(a) // a=20
}
console.log(a)  // a =10;
const a = 30;     // Error - redeclaration of const a
console.log(a)


let  vs. const

let a; // undefined
const a; // Error



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