function foo() {
  console.log(functionScope); // undefined
  {
      var functionScope = 'functionScope';
  }
  console.log(functionScope); // 'functionScope'


  // let
  {
    let blockScopeLet = 'blockScopeLet';
    console.log(blockScopeLet); // 'blockScopeLet'

    blockScopeLet = 'reAssignBlockScopeLet';
    console.log(blockScopeLet); // 'reAssignBlockScopeLet'
  }

  //console.log(blockScopeLet); // ReferenceError

  // const
  {
    const blockScopeConst = 'blockScopeConst';
    console.log(blockScopeConst); // 'blockScopeConst'

    // blockScopeConst = 'reAssignBlockScopeConst'; // TypeError
  }

  // console.log(blockScopeConst); // ReferenceError
}

foo();