docs: function (str) {
              
              var typeOf = typeof str;
              if (typeOf === 'number')
                  return str;
              
              else if (typeOf !== 'string')
                  return Number.NaN;
              
              else if (_floatRegex.test(str))
                  return parseFloat(str);
                  
              else if (   str === 'Infinity'
                       || str === '+Infinity' )
                  return Number.POSITIVE_INFINITY;
              
              else if (str === '-Infinity')
                  return Number.NEGATIVE_INFINITY;
              
              else  // whether "NaN" or any other string
                  return Number.NaN;
          }