JSFiddle - React, Tailwind, and code Playground

HTML

<form id="myform">
    <input id="firstfield" name="firstfield" class="captureKeys" value="100" type="text" />
    <input id="secondfield" name="secondfield" class="captureKeys" value="200" type="text" />
</form>
<a href="#">Dummy link for final tabindex</a>

CSS

#myform input[type="text"] {
    border: 1px solid #DBDAD7;
    box-shadow: 1px 1px 4px #F4F4F4 inset;
    font-size: 14px;
    height: 47px;
    line-height: 46px;
    padding: 0 10px;
    margin: 0;
}
.focus {background:#e6e9f0;}

JavaScript

jQuery(document).ready(function() {
    (function($) {
        $.fn.keyAction = function(theKey) {
            return this.each(function() {
                if ($(this).hasClass("captureKeys")) {
                    alert("Handler for " + $(this).attr("id") + " .keyup() called with key "+ theKey + ".");
                    // KeyCode dependent statements go here.
                }
            });
        };
    })(jQuery);
    
    $(".captureKeys").on("keydown", function(e) {
        $("*").removeClass("focus");
        $(this).addClass("focus");
    });
    $("body").on("keyup", "*:focus", function(e) {
        if (e.which == 9) {
            $(".focus.captureKeys").keyAction(e.which);
            $("*").removeClass("focus");
        }
        else {
            $(this).keyAction(e.which);
        }
    });
});