Ternary operator function for JavaScript 'get middle letter' Code War challenge

Question

Code challenge: write a function that gets the middle letter(s) of a string of even or odd numbered letters, as a ternary operator.

My function is working for odd numbers. But it does not work for even numbers - it seems to be skipping letters.

eg.

getMiddle("testing") // the output is "t", this is correct.  
getMiddle("test") // the output is "et", it should be "es". 

my code:

    function getMiddle(str) {
     return str.length % 2 === 0 ? str[str.length/2 - 1] + str[str.length/2 + 1] : str[Math.floor(str.length/2)];
    }

Answer 1

When the length is is even, you want the 2 characters which are at the middle. You do that by taking the length of the string and divide it by 2.

That index in a zero based array will be the s.If you subtract 1 from the index, it will be the e. When you add +1, you get the t

In your code, you concatenate the index -1 and the index +1 leading to et

You should omit the + 1 in str[str.length/2 + 1] like:

function getMiddle(str) {
    return str.length % 2 === 0 ? str[str.length / 2 - 1] + str[str.length / 2] : str[Math.floor(str.length / 2)];
}

function getMiddle(str) {
  return str.length % 2 === 0 ? str[str.length / 2 - 1] + str[str.length / 2] : str[Math.floor(str.length / 2)];
}

console.log(getMiddle("testing"));
console.log(getMiddle("test"));
console.log(getMiddle("testtest"))