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

// HTML

<input type="text" class="decimal" value="" />

            

 or

<asp:TextBox ID="txt_actID" runat="server">

///////  JS

$('input').on('keydown', function (event) {

                return isNumber(event, this);

            });

            function isNumber(evt, element) {

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

                if ((charCode != 190 || $(element).val().indexOf('.') != -1) && (charCode != 110 || $(element).val().indexOf('.') != -1)

                && ((charCode < 48 && charCode != 8) || (charCode > 57 && charCode < 96) || charCode > 105))

                    return false;

                return true;

            }

/////////////////or

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

/// js

 function isNumber(evt, element) {

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

                if ((charCode != 190 || $(element).val().indexOf('.') != -1) && (charCode != 110 || $(element).val().indexOf('.') != -1)

                && ((charCode < 48 && charCode != 8) || (charCode > 57 && charCode < 96) || charCode > 105))

                    return false;

                return true;

            }