function nextChar(char) {
return String.fromCharCode(char.charCodeAt(0) + 1);
}
console.log(nextChar('a'));
console.log(nextChar('b'));
console.log(nextChar('c'));
console.log(nextChar('d'));
console.log(nextChar('A'));
console.log(nextChar('B'));
console.log(nextChar('C'));
console.log(nextChar('D'));
/*
run:
b
c
d
e
B
C
D
E
*/