Javascript: Find out previous letter in alphabet

Question

If I got a Letter in JavaScript, I'd like to find out the previous letter in alphabetic order, so if input is "C", output must be "B". Are there any standard solutions or do i have to create some special functions?

Answer 1

var ch = 'b';
String.fromCharCode(ch.charCodeAt(0) - 1); // 'a'

And if you wanted to loop around the alphabet just do a check specifically for 'a' -- loop to 'z' if it is, otherwise use the method above.