Given a string, replace every single-digit number (0-9) with its English word equivalent. Non-digit characters and multi-digit numbers should be left unchanged.
Function Signature
numToText(str)
Parameters
str — a string that may contain single-digit numbers.
Output
Return a new string with single-digit numbers replaced by words.
Constraints
The function must use recursion.
The function should accept exactly one argument.
Examples
numToText('5 dogs and 6 ponies') → 'five dogs and six ponies'
numToText('Give me 8 dollars') → 'Give me eight dollars'