Untitled

document.addEventListener("DOMContentLoaded", () => {
    const INFERNUS = document.getElementById("INFERNUS"); // <button> in index.html
    INFERNUS.addEventListener("click", () => {
        mp.gui.chat.push("GET INFERNUS");
    })
});

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
</head>
<script src="./handler.js"></script>
<body>
    <div class="container">
        <p class="mainBlock">Car Spawner</p>
        <div id="car">INFERNUS<button id="INFERNUS>Got it!</button></div>
    </div>
</body>
</html>