Enter jquery mask number

Question

Enter jquery mask number

I use the function to mask the entered number in the text box, but I want to assign a value before masking its observed knockout. I'm not sure where in my function I can capture and save this value, because when you enter a value in a text field and set, the values are replaced with "*", as it is intended only for display. Therefore, when my text box displays *** 111, my observable should have the value 1111111.

    var viewModel = function () {
        $(".textboxsemimedium").on("keydown keyup",
            function (e) {
              
                $(this).prop("value",
                    function (i, o) {
                        if (o.length < 6) {
                      
                            return o.replace(/\d/g, "*");
                        }
                    });
            });
        self.theMemberNo = ko.observable();
    }
    ko.applyBindings(viewModel);

<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
            <input class="textboxsemimedium" data-bind="value:theMemberNo"  data-val="true" data-val-length="Member Number be of 9 characters!" data-val-length-max="9" data-val-length-min="9" data-val-required="Member Number is required!" id="MemberNumber" maxlength="10" name="MemberNumber" title="Member Number is Required!" type="text" value="">
<span data-bind="text:theMemberNo"></span>