The charAt method returns a character value equal to the character at the specified index. The first character in a string is at index 0, the second is at index 1, and so forth. Values of index out of valid range return an empty string.
function charAtTest(n){
var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; // Initialize variable.
var s; // Declare variable.
s = str.charAt(n - 1); // Get correct character
// from position n – 1.
return(s); // Return character.
}