JSFiddle - React, Tailwind, and code Playground

HTML

<div id="message">some message</div>

<input type="text" id="myInput" />

JavaScript

$("#message").hide();

var prefix = ['HX', 'HD', 'BD', 'LS']

$('#myInput').keyup(function(e) {
    var value = $(this).val();
    var firstTwo = value.substr(0,2).toUpperCase();
    if(value.length > 1 && ($.inArray(firstTwo, prefix) >= 0)) {
        $("#message:hidden").fadeIn();
    }
});