Using `let` in loop

let_for_loop.js

var arr = new Array(3);
 
for (var i = 0; i<arr.length; i++) {
  console.log(i); // 0,1,2,3
}
 
console.log(i); // 3
 
for(let j = 0; j < arr.length; j++){}
 
console.log(j); //ReferenceError: j is not defined