This feature is also there in C and C++ and probably other languages. The catch is that js seems to have inherited the syntax but not the scoping rules.

  const a = 5;
  console.log(a)
  {
    const a = 10;
    console.log(a)
  }
  console.log(a)

  5 
  10 
  5

  const a = do {
    if (b) { 5 } else { 10 }
  };