code: function ( num1, num2 ) {
  		if ( isNaN( num1 ) || isNaN( num2 ) ) {
  			throw new Error( label.error.expectedNumber );
  		}
  
  		return Math.abs( num1 - num2 );
  	}
docs: Returns the difference of arg
  
  @method odd
  @param {Number} arg Number to compare
  @return {Number}    The absolute difference