var-vs-let

global variables are variables that are defined outside of any functions

global variables should be defined by let, do not use var for global functions

let name = "John";

console.log(name) ✅
    

let variables don't exist outside the block scope

if we try to console.log(i) outside that block it won't be defined

for (let i = 1; i <= 3; i += 1) {
  console.log(i);
}

console.log(i) ❌
    

var is not limited by the block scope so we can access it even after for loop ends

for (var j = 1; j <= 3; j += 1) {
  console.log(j);
}

console.log(j) ✅
    

var can be limited by a function

var is not accessible outside of that function

myFunction();
function myFunction() {
  for (var k = 1; k <= 3; k += 1) {
    console.log(k);
  }
}
console.log(k) ❌