let, var, const

letconst.js

//how we can use var
if(true) {
  var t = 9;
}
console.log(t) //prints 9

//how we use let
let t1 = 9;
if(true) {
  let t1 = 10;
  console.log(t1); //prints 10
}
console.log(t1); //prints 9

//use of const
const t3 = 10;
t3 = 11; //error