Get the Middle Character (JavaScript)

getMiddle.js

// Awesome
function getMiddle(s)
{
  return s.substr(Math.ceil(s.length / 2 - 1), s.length % 2 === 0 ? 2 : 1);
}

// Usual
function GetMiddle(s)
{
    var middle = Math.floor(s.length/2);
    if (s.length % 2 == 0)
        return s[middle-1] + s[middle];
    else
        return s[middle];
}

/*
Kata.getMiddle("test") should return "es"
Kata.getMiddle("testing") should return "t"
Kata.getMiddle("middle") should return "dd"
Kata.getMiddle("A") should return "A"
*/

Thanks for the explications :)