code: function subtract(minuend, subtrahend) {
          var result;
          if (minuend === undefined && subtrahend === undefined) {
            return 0;
          }
          if (minuend !== undefined) {
            result = minuend;
          }
          if (subtrahend !== undefined) {
            result = result === undefined ? subtrahend : result - subtrahend;
          }
          return result;
        }
docs: Subtract two numbers.
  
  @static
  @memberOf _
  @category Math
  @param {number} minuend The first number in a subtraction.
  @param {number} subtrahend The second number in a subtraction.
  @returns {number} Returns the difference.
  @example
  
  _.subtract(6, 4);
  // => 2