priority let by var

index.js

{
  var x = 1
  {
    let x = 2 // SyntaxError: Identifier 'x' has already been declared
    {
      function f(){
        let x = 10
        {
          var x = 20 // SyntaxError: Identifier 'x' has already been declared
          {
            console.log('fscope3 x = ', x);
          }
          console.log('fscope2 x = ', x);
        }
        console.log('fscope1 x = ', x);
      }
      f()
      console.log('scope1 x = ', x);
    }
    console.log('scope2 x = ', x);
  }
  console.log('scope3 x = ', x);
}