let scope

index.js

{ 
  var x = 11
  {
    let x = 10
    {
      console.log('x (unknown) = ', x); // can you guess which x here?
      function f() {
        var a = 1
        {
          var a = 2
          {
            var a = 30
          }
          console.log('a = ', a); // 30
        }
        console.log('a = ', a); // 30
      }
      f()
    }
    console.log('x = ', x); // 30
  }
  console.log('x = ', x); // 30
}