code: function /* 9.2.10 */$$core$$GetNumberOption (options, property, minimum, maximum, fallback) {
          var
              // 1. Let value be the result of calling the [[Get]] internal method of
              //    options with argument property.
              value = options[property];
  
          // 2. If value is not undefined, then
          if (value !== undefined) {
              // a. Let value be ToNumber(value).
              value = Number(value);
  
              // b. If value is NaN or less than minimum or greater than maximum, throw a
              //    RangeError exception.
              if (isNaN(value) || value < minimum || value > maximum)
                  throw new RangeError('Value is not a number or outside accepted range');
  
              // c. Return floor(value).
              return Math.floor(value);
          }
          // 3. Else return fallback.
          return fallback;
      }
docs: The GetNumberOption abstract operation extracts a property value from the
  provided options object, converts it to a Number value, checks whether it is
  in the allowed range, and fills in a fallback value if necessary.