how to change numeric value to words in javascript

<div>
        Enter Numbers (0-1000) :
        <asp:TextBox ID="txtnumbers" runat="server"></asp:TextBox>
        <asp:Button ID="btnConvert" Text="Convert" runat="server"
            onclick="btnConvert_Click" /><br />
        In Words :
        <asp:Label ID="lblNumberWords" runat="server" Text=""></asp:Label>
    </div>

protected void btnConvert_Click(object sender, EventArgs e)
    {
        StringBuilder sb = new StringBuilder();
        int no = int.Parse(txtnumbers.Text);
        int length = txtnumbers.Text.Trim().Length;
        for (int index = length; index > 0; index--)
        {
            if (index == 1)
            {
                sb.Append(convertToWord(no));
            }
            else
            {
                int dig = no / (Power(index));
                no = no % (Power(index));
                sb.Append(convertToWord(dig)+" ");
            }
        }
        lblNumberWords.Text = sb.ToString();
    }
    private int Power(int index)
    {
        int res=1;
        if (index == 1) ;
        else
            res = 10 * Power(index - 1);
        return res;
    }
    private string convertToWord(int digit)
    {
        switch (digit)
        {
            case 1:
                return "one";
            case 2:
                return "two";
            case 3:
                return "three";
            case 4:
                return "four";
            case 5:
                return "five";
            case 6:
                return "six";
            case 7:
                return "seven";
            case 8:
                return "eight";
            case 9:
                return "nine";
        }
        return "Enter Digits!";
    }