advanced_javascript.md

###var vs let vs const var is only used for backward compatibility with plain javascript (ES5 and before) "var" variables are visible outside the block scope

var m = "hello";
if (m){
  var i:number;
  for(i=0; i<3;i++){
    console.log(m + ' ' + i)
  }
}
console.log(i); // outputs 2

"let" variables are not visible outsidde the block scope

var m = "hello";
if (m){
  let i:number;
  for(i=0; i<3;i++){
    console.log(m + ' ' + i)
  }
}
console.log(i) //undefined

"const" variables is one of the best practices because creates an inmutable reference,

const  m = "hello";