Printing the next character

Given a string, replace every letter with its subsequent letter. For example, the letter A will be converted to letter B.

Sample Code:

function nextTerm(str) {
// Enter your logic here...
}

Examples:

Input: 'abcd'
Output: 'bcde'
Explanation: The subsequent letter 'a' is 'b'.

Input: 'bncd'
Output: 'code'
Explanation: The subsequent letter 'b' is 'c'.