Define a recursive function isEven in JS

isEven.js

/*Define a recursive function isEven corresponding to this description. 
 The function should accept a number parameter and return a Boolean.
 Test it on 5 and 68. See how it behaves on -1...-22... */
 
 var isEven = function(num) {
   num = Math.abs(num); // convert to absolute value to account to negative numbers
   // Why I used Math.abs() see here: http://devdocs.io/javascript/global_objects/math/abs
   if (num === 0)
     return true;
   else if (num === 1)
     return false;
  else
    return isEven(num -2);
     
}

console.log(isEven(5));
// → false
console.log(isEven(68));
// → true
console.log(isEven(-1));
// → false
console.log(isEven(-22));
// → true