MVC TextBoxFor的输入字段中只有4位数字

Question

I have an MVC5 project and I have an input field that I only want to take an 8 digit number. I tried implementing it like this:

@Html.TextBoxFor(model => model.oldPin, new { maxlength = "8", @class = "form-control disablecopypaste", onkeydown = "return isNumber(event);" })

 function isNumber(evt) {
        evt = (evt) ? evt : window.event;
        var charCode = (evt.which) ? evt.which : evt.keyCode;

        if (charCode === 16) {
            return false;
        }
        if (charCode > 31 && (charCode < 48 || charCode > 57)) {
            return false;
        }
        return true;
    }

My problem is that while this prevents numbers it allows spaces and special characters. How do I prevent this? It works with the keypress event but its depreciated and I'm concerned about browser compatibility. Is there any way to do this with the keydown event? All the answers I've seen are all with the keypress event.

Answer 1

 function allowNumberOnly (e) { var ascii = (e.which) ? e.which : e.keyCode if (ascii> 31 && (ascii< 48 || ascii> 57)) { return false; } else { var vall = $('#oldPin').val() if (vall.length > 3) { return false; } else { return true; } } }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <input class="form-control " id="oldPin" name="oldPin" onkeypress="return allowNumberOnly(event)" type="text" value="">