JavaScript : Restrict multiple time entry of and char or number or decimal using javascript on keypress

// HTML

<asp:TextBox ID="TextBox1" runat="server"   onkeypress="return isNumber(this, event);">

// JS

<script type="text/javascript">

function Is_Double_Exits(obj, event) {

            debugger;

            var charCode = (event.which) ? event.which : event.keyCode;

            if (charCode == 46) {   // keycode of decimal

                if (obj.value.indexOf('.') === -1) {

                    return true;

                }

                else {

                    return false;

                }

            }

            else {

                if (charCode > 31 && (charCode < 48 || charCode > 57)) {

                    return false;

                }

                else {

                    return true;

                }

            }

return true;

        }

</script>