Comment by z3t4

Type systems do not thinking for you, you still have to make a type with a range check. So you could just as well write

  function foo(n) {
    if(n < 10 || n > 100) throw new Error("Expected n=" + n + " to be between 10 and 100");
    return n*2;
  }

And while you are at it you can write an unit test that is tested at compile time or in the editor/IDE.

  // assert(foo(10),20);