JS newbie here. I want to write a basic program that changes each element in a string based on a condition. If the letter is uppercase we swap it to lowercase, if the letter is already lowercase we swap it to uppercase. Why is this not working? Thanks!

```
function SwapCase(str){

for (var i = 0; i < str.length; i++) {
    if (str.charAt(i)===str.charAt(i).toUpperCase()) {
       str.charAt(i).toLowerCase();
    } else{}
       str.charAt(i).toUpperCase();
    }

return str;

}

SwapCase("gEORGE");

```