/*
Problem statement
=================

Here’s another way to define whether a positive whole number is even or odd:

• Zero is even.
• One is odd.
• For any other number N, its evenness is the same as N - 2.

Define a recursive function isEven corresponding to this description. The function should accept a number parameter and return a Boolean.
Test it on 50 and 75. See how it behaves on -1. Why? Can you think of a way to fix this?

*/

function isEven(num1){
  if(isNaN(num1)){
    return 'Not a number!';
  }
  else if(num1 == 0){
    return 'even';
  }
  else if(num1 == 1){
    return 'odd';
  }
  else{
    if(num1 > 0){
       return deduct(num1 - 2);
    }
    else{
      return deduct(num1 + 2);
    }
  }
  function deduct(num2){
    return isEven(num2);
  }
}

console.log('Entered number is: ' + isEven(0));
console.log('Entered number is: ' + isEven(1));
console.log('Entered number is: ' + isEven(50));
console.log('Entered number is: ' + isEven(75));
console.log('Entered number is: ' + isEven(-50));
console.log('Entered number is: ' + isEven(-75));
console.log('Entered number is: ' + isEven('lorem'));

/*
Output
======

"Entered number is: even"
"Entered number is: odd"
"Entered number is: even"
"Entered number is: odd"
"Entered number is: even"
"Entered number is: odd"
"Entered number is: Not a number!"

*/