ThisobToDouble() private static method

private static ThisobToDouble ( Object thisob ) : double
thisob Object
return double
        public static String toExponential(Object thisob, Object fractionDigits)
        {
            double value = NumberPrototype.ThisobToDouble(thisob);
            double f;

            if (fractionDigits == null || fractionDigits is Missing)
            {
                f = 16;
            }
            else
            {
                f = Convert.ToInteger(fractionDigits);
            }
            if (f < 0 || f > 20)
            {
                throw new JScriptException(JSError.FractionOutOfRange);
            }
            StringBuilder fmt = new StringBuilder("#.");

            for (int i = 0; i < f; i++)
            {
                fmt.Append('0');
            }
            fmt.Append("e+0");
            return(value.ToString(fmt.ToString(), CultureInfo.InvariantCulture));
        }
        public static String toPrecision(Object thisob, Object precision)
        {
            double value = NumberPrototype.ThisobToDouble(thisob);

            if (precision == null || precision is Missing)
            {
                return(Convert.ToString(value));
            }
            double df = Convert.ToInteger(precision);

            if (df < 1 || df > 21)
            {
                throw new JScriptException(JSError.PrecisionOutOfRange);
            }
            int f = (int)df;

            if (Double.IsNaN(value))
            {
                return("NaN");
            }
            if (Double.IsInfinity(value))
            {
                return(value > 0.0 ? "Infinity" : "-Infinity");
            }
            String sign;

            if (value >= 0.0)
            {
                sign = "";
            }
            else
            {
                sign  = "-";
                value = -value;
            }
            String mant = value.ToString("e" + (f - 1).ToString(), CultureInfo.InvariantCulture);
            int    exp  = Int32.Parse(mant.Substring(mant.Length - 4), CultureInfo.InvariantCulture);

            mant = mant.Substring(0, 1) + mant.Substring(2, f - 1);
            if (exp >= f || exp < -6)
            {
                return(sign + mant.Substring(0, 1) + (f > 1 ? "." + mant.Substring(1) : "")
                       + (exp >= 0 ? "e+" : "e") + exp.ToString());
            }
            if (exp == f - 1)
            {
                return(sign + mant);
            }
            if (exp >= 0)
            {
                return(sign + mant.Substring(0, exp + 1) + "." + mant.Substring(exp + 1));
            }
            return(sign + "0." + mant.PadLeft(f - exp - 1, '0'));
        }
        public static String toFixed(Object thisob, double fractionDigits)
        {
            double value = NumberPrototype.ThisobToDouble(thisob);

            if (Double.IsNaN(fractionDigits))
            {
                fractionDigits = 0;
            }
            else if (fractionDigits < 0 || fractionDigits > 20)
            {
                throw new JScriptException(JSError.FractionOutOfRange);
            }
            return(value.ToString("f" + ((int)fractionDigits).ToString(CultureInfo.InvariantCulture), CultureInfo.InvariantCulture));
        }