Write a method that takes an array of consecutive (increasing) letters as input and that returns the missing letter in the array js.
function fearNotLetter(str) {
var string = array. join("");
for (var i = 0; i < string. length; i++) {
if (string. charCodeAt(i + 1) - string. charCodeAt(i) != 1) {
return String. fromCharCode(string. charCodeAt(i) + 1);
}
}
return undefined
}