JSFiddle - React, Tailwind, and code Playground

HTML

<form><input id="testInput" size="30"/></form>

    <div id="btn">E</div>

CSS

#btn {
    font: 24px "Trebuchet MS",sans-serif;
    color: white;
    text-align: center;
    width: 20px;
    height: 20px;
    margin: 10px;
    padding: 20px;
    background-color: #34ab22;
}

JavaScript

var press = jQuery.Event("keydown");
press.which = 69; // # Some key code value
press.keyCode = 69;
press.target = $('#testInput');


$(document).on('keydown', function(event) {
    alert(event.keyCode);
});

$('#btn').click( function() {
    $('#testInput').focus();
	$(document).trigger(press);
	console.info(press);
});